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Riemann Sums Rectangle Approximations Trapeziodal and Parabolic Approximations Lecture 11 Section 8.7 Numerical Integration Jiwen He Department of Mathematics, University of Houston [email protected] http://math.uh.edu/jiwenhe/Math1432 Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 1 / 14

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Page 1: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic Approximations

Lecture 11Section 8.7 Numerical Integration

Jiwen He

Department of Mathematics, University of Houston

[email protected]://math.uh.edu/∼jiwenhe/Math1432

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 1 / 14

Page 2: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsArea Problem Lower and Upper Sums Riemann Sum

Area Problem

Partition of [a, b]

Take a partition P = x0, x1, · · · , xn of [a, b]. Then P splits upthe interval [a, b] into a finite number of subintervals [x0, x1], · · · ,[xn−1, xn] with a = x0 < x1 < · · · < xn = b. We have

[a, b] = [x0, x1] ∪ · · · ∪ [xi−1, xi ] ∪ · · · ∪ [xn−1, xn]

Remark

This breaks up the region Ω into n subregions Ω1,· · · ,Ωn:Ω = Ω1 ∪ · · · ∪ Ωi ∪ · · · ∪ Ωn

We can estimate the total area of Ω by estimating the area of eachsubregion Ωi and adding up the results.

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 2 / 14

Page 3: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsArea Problem Lower and Upper Sums Riemann Sum

Area Problem

Partition of [a, b]

Take a partition P = x0, x1, · · · , xn of [a, b]. Then P splits upthe interval [a, b] into a finite number of subintervals [x0, x1], · · · ,[xn−1, xn] with a = x0 < x1 < · · · < xn = b. We have

[a, b] = [x0, x1] ∪ · · · ∪ [xi−1, xi ] ∪ · · · ∪ [xn−1, xn]

Remark

This breaks up the region Ω into n subregions Ω1,· · · ,Ωn:Ω = Ω1 ∪ · · · ∪ Ωi ∪ · · · ∪ Ωn

We can estimate the total area of Ω by estimating the area of eachsubregion Ωi and adding up the results.

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 2 / 14

Page 4: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsArea Problem Lower and Upper Sums Riemann Sum

Lower and Upper Sums

Let ∆xi = xi − xi−1, mi = minx∈[xi−1,xi ]

f (x), Mi = maxx∈[xi−1,xi ]

f (x)

mi∆xi = area of ri ≤ area of Ωi ≤ area of Ri = Mi∆xi

Lf (P) :=n∑

i=1

mi∆xi ≤ I =

∫ b

af (x) dx ≤

n∑i=1

Mi∆xi =: Uf (P)

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 3 / 14

Page 5: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsArea Problem Lower and Upper Sums Riemann Sum

Lower and Upper Sums

Let ∆xi = xi − xi−1, mi = minx∈[xi−1,xi ]

f (x), Mi = maxx∈[xi−1,xi ]

f (x)

mi∆xi = area of ri ≤ area of Ωi ≤ area of Ri = Mi∆xi

Lf (P) :=n∑

i=1

mi∆xi ≤ I =

∫ b

af (x) dx ≤

n∑i=1

Mi∆xi =: Uf (P)

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 3 / 14

Page 6: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsArea Problem Lower and Upper Sums Riemann Sum

Lower and Upper Sums

Let ∆xi = xi − xi−1, mi = minx∈[xi−1,xi ]

f (x), Mi = maxx∈[xi−1,xi ]

f (x)

mi∆xi = area of ri ≤ area of Ωi ≤ area of Ri = Mi∆xi

Lf (P) :=n∑

i=1

mi∆xi ≤ I =

∫ b

af (x) dx ≤

n∑i=1

Mi∆xi =: Uf (P)

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 3 / 14

Page 7: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsArea Problem Lower and Upper Sums Riemann Sum

Riemann Sum

Riemann Sum

S∗(P) = f (x∗1 )∆x1 + f (x∗2 )∆x2 + · · ·+ f (x∗n )∆xn

where x∗i is any point picked in [xi−1, xi ] for i = 1, · · · , n. Wehave

Lf (P) :=n∑

i=1

mi∆xi ≤ S∗(P) :=n∑

i=1

f (x∗i )∆xi ≤n∑

i=1

Mi∆xi =: Uf (P)

Limit of Riemann Sums∫ b

af (x) dx = lim

|P|→0[f (x∗1 )∆x1 + f (x∗2 )∆x2 + · · ·+ f (x∗n )∆xn]

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 4 / 14

Page 8: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsArea Problem Lower and Upper Sums Riemann Sum

Riemann Sum

Riemann Sum

S∗(P) = f (x∗1 )∆x1 + f (x∗2 )∆x2 + · · ·+ f (x∗n )∆xn

where x∗i is any point picked in [xi−1, xi ] for i = 1, · · · , n. Wehave

Lf (P) :=n∑

i=1

mi∆xi ≤ S∗(P) :=n∑

i=1

f (x∗i )∆xi ≤n∑

i=1

Mi∆xi =: Uf (P)

Limit of Riemann Sums∫ b

af (x) dx = lim

|P|→0[f (x∗1 )∆x1 + f (x∗2 )∆x2 + · · ·+ f (x∗n )∆xn]

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 4 / 14

Page 9: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsArea Problem Lower and Upper Sums Riemann Sum

Riemann Sum

Riemann Sum

S∗(P) = f (x∗1 )∆x1 + f (x∗2 )∆x2 + · · ·+ f (x∗n )∆xn

where x∗i is any point picked in [xi−1, xi ] for i = 1, · · · , n. Wehave

Lf (P) :=n∑

i=1

mi∆xi ≤ S∗(P) :=n∑

i=1

f (x∗i )∆xi ≤n∑

i=1

Mi∆xi =: Uf (P)

Limit of Riemann Sums∫ b

af (x) dx = lim

|P|→0[f (x∗1 )∆x1 + f (x∗2 )∆x2 + · · ·+ f (x∗n )∆xn]

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 4 / 14

Page 10: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsArea Problem Lower and Upper Sums Riemann Sum

Riemann Sum

Riemann Sum

S∗(P) = f (x∗1 )∆x1 + f (x∗2 )∆x2 + · · ·+ f (x∗n )∆xn

where x∗i is any point picked in [xi−1, xi ] for i = 1, · · · , n. Wehave

Lf (P) :=n∑

i=1

mi∆xi ≤ S∗(P) :=n∑

i=1

f (x∗i )∆xi ≤n∑

i=1

Mi∆xi =: Uf (P)

Limit of Riemann Sums∫ b

af (x) dx = lim

|P|→0[f (x∗1 )∆x1 + f (x∗2 )∆x2 + · · ·+ f (x∗n )∆xn]

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 4 / 14

Page 11: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsRegular Partition Approximations Error Estimates

Regular Partition

Problem

Find the approximate value of

ln 2 =

∫ 2

1

dx

xusing only the values of f (x) = 1

x at

1,6

5,

7

5,

8

5,

9

5, 2.

Numerical Integration

Approximate∫ ba f (x) dx using only values of f at n + 1

equally-spaced points between a and b.

Regular Partition of [a, b]

Let xi = a + i∆x , i = 0, 1, · · · , n, where ∆x = b−an . Then

[a, b] = [x0, x1] ∪ · · · ∪ [xi−1, xi ] ∪ · · · ∪ [xn−1, xn]

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 5 / 14

Page 12: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsRegular Partition Approximations Error Estimates

Regular Partition

Problem

Find the approximate value of

ln 2 =

∫ 2

1

dx

xusing only the values of f (x) = 1

x at

1,6

5,

7

5,

8

5,

9

5, 2.

Numerical Integration

Approximate∫ ba f (x) dx using only values of f at n + 1

equally-spaced points between a and b.

Regular Partition of [a, b]

Let xi = a + i∆x , i = 0, 1, · · · , n, where ∆x = b−an . Then

[a, b] = [x0, x1] ∪ · · · ∪ [xi−1, xi ] ∪ · · · ∪ [xn−1, xn]

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 5 / 14

Page 13: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsRegular Partition Approximations Error Estimates

Regular Partition

Problem

Find the approximate value of

ln 2 =

∫ 2

1

dx

xusing only the values of f (x) = 1

x at

1,6

5,

7

5,

8

5,

9

5, 2.

Numerical Integration

Approximate∫ ba f (x) dx using only values of f at n + 1

equally-spaced points between a and b.

Regular Partition of [a, b]

Let xi = a + i∆x , i = 0, 1, · · · , n, where ∆x = b−an . Then

[a, b] = [x0, x1] ∪ · · · ∪ [xi−1, xi ] ∪ · · · ∪ [xn−1, xn]

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 5 / 14

Page 14: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsRegular Partition Approximations Error Estimates

Rectangle Approximations

∫ xi

xi−1f (x) dx f (xi−1)∆x f (xi )∆x f

(xi−1+xi

2

)∆x

Rectangle Approximations of∫ xi

xi−1f (x) dx

f (xi−1)∆x , f (xi )∆x , f(

xi−1+xi

2

)∆x

left-endpoints right-endpoints midpoints

Rectangle Approximations of∫ ba f (x) dx =

∑ni=1

∫ xi

xi−1f (x) dx

n∑i=1

f (xi−1)∆x ,

n∑i=1

f (xi )∆x ,

n∑i=1

f

(xi−1 + xi

2

)∆x

left-endpoints right-endpoints midpoints

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 6 / 14

Page 15: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsRegular Partition Approximations Error Estimates

Rectangle Approximations

∫ xi

xi−1f (x) dx f (xi−1)∆x f (xi )∆x f

(xi−1+xi

2

)∆x

Rectangle Approximations of∫ xi

xi−1f (x) dx

f (xi−1)∆x , f (xi )∆x , f(

xi−1+xi

2

)∆x

left-endpoints right-endpoints midpoints

Rectangle Approximations of∫ ba f (x) dx =

∑ni=1

∫ xi

xi−1f (x) dx

n∑i=1

f (xi−1)∆x ,

n∑i=1

f (xi )∆x ,

n∑i=1

f

(xi−1 + xi

2

)∆x

left-endpoints right-endpoints midpoints

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 6 / 14

Page 16: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsRegular Partition Approximations Error Estimates

Rectangle Approximations

∫ xi

xi−1f (x) dx f (xi−1)∆x f (xi )∆x f

(xi−1+xi

2

)∆x

Rectangle Approximations of∫ xi

xi−1f (x) dx

f (xi−1)∆x , f (xi )∆x , f(

xi−1+xi

2

)∆x

left-endpoints right-endpoints midpoints

Rectangle Approximations of∫ ba f (x) dx =

∑ni=1

∫ xi

xi−1f (x) dx

n∑i=1

f (xi−1)∆x ,

n∑i=1

f (xi )∆x ,

n∑i=1

f

(xi−1 + xi

2

)∆x

left-endpoints right-endpoints midpoints

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 6 / 14

Page 17: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsRegular Partition Approximations Error Estimates

Rectangle Approximations

∫ xi

xi−1f (x) dx f (xi−1)∆x f (xi )∆x f

(xi−1+xi

2

)∆x

Rectangle Approximations of∫ xi

xi−1f (x) dx

f (xi−1)∆x , f (xi )∆x , f(

xi−1+xi

2

)∆x

left-endpoints right-endpoints midpoints

Rectangle Approximations of∫ ba f (x) dx =

∑ni=1

∫ xi

xi−1f (x) dx

n∑i=1

f (xi−1)∆x ,

n∑i=1

f (xi )∆x ,

n∑i=1

f

(xi−1 + xi

2

)∆x

left-endpoints right-endpoints midpoints

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 6 / 14

Page 18: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsRegular Partition Approximations Error Estimates

Rectangle Approximations

∫ xi

xi−1f (x) dx f (xi−1)∆x f (xi )∆x f

(xi−1+xi

2

)∆x

Rectangle Approximations of∫ xi

xi−1f (x) dx

f (xi−1)∆x , f (xi )∆x , f(

xi−1+xi

2

)∆x

left-endpoints right-endpoints midpoints

Rectangle Approximations of∫ ba f (x) dx =

∑ni=1

∫ xi

xi−1f (x) dx

n∑i=1

f (xi−1)∆x ,

n∑i=1

f (xi )∆x ,

n∑i=1

f

(xi−1 + xi

2

)∆x

left-endpoints right-endpoints midpoints

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 6 / 14

Page 19: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsRegular Partition Approximations Error Estimates

Rectangle Approximations

∫ xi

xi−1f (x) dx f (xi−1)∆x f (xi )∆x f

(xi−1+xi

2

)∆x

Rectangle Approximations of∫ xi

xi−1f (x) dx

f (xi−1)∆x , f (xi )∆x , f(

xi−1+xi

2

)∆x

left-endpoints right-endpoints midpoints

Rectangle Approximations of∫ ba f (x) dx =

∑ni=1

∫ xi

xi−1f (x) dx

n∑i=1

f (xi−1)∆x ,

n∑i=1

f (xi )∆x ,

n∑i=1

f

(xi−1 + xi

2

)∆x

left-endpoints right-endpoints midpoints

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 6 / 14

Page 20: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsRegular Partition Approximations Error Estimates

Rectangle Approximations

∫ xi

xi−1f (x) dx f (xi−1)∆x f (xi )∆x f

(xi−1+xi

2

)∆x

Rectangle Approximations of∫ xi

xi−1f (x) dx

f (xi−1)∆x , f (xi )∆x , f(

xi−1+xi

2

)∆x

left-endpoints right-endpoints midpoints

Rectangle Approximations of∫ ba f (x) dx =

∑ni=1

∫ xi

xi−1f (x) dx

n∑i=1

f (xi−1)∆x ,

n∑i=1

f (xi )∆x ,

n∑i=1

f

(xi−1 + xi

2

)∆x

left-endpoints right-endpoints midpoints

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 6 / 14

Page 21: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsRegular Partition Approximations Error Estimates

Rectangle Approximations

∫ xi

xi−1f (x) dx f (xi−1)∆x f (xi )∆x f

(xi−1+xi

2

)∆x

Rectangle Approximations of∫ xi

xi−1f (x) dx

f (xi−1)∆x , f (xi )∆x , f(

xi−1+xi

2

)∆x

left-endpoints right-endpoints midpoints

Rectangle Approximations of∫ ba f (x) dx =

∑ni=1

∫ xi

xi−1f (x) dx

n∑i=1

f (xi−1)∆x ,

n∑i=1

f (xi )∆x ,

n∑i=1

f

(xi−1 + xi

2

)∆x

left-endpoints right-endpoints midpoints

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 6 / 14

Page 22: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsRegular Partition Approximations Error Estimates

Rectangle Rules

Rectangle Rule for Approximating∫ ba f (x) dx

Left-endpoint rule:

Ln =b − a

n[f (x0) + f (x1) + · · ·+ f (xn−1)]

Right-endpoint rule:

Rn =b − a

n[f (x1) + f (x2) + · · ·+ f (xn)]

Midpoint rule:

Mn =b − a

n

[f

(x0 + x1

2

)+ · · ·+ f

(xn−1 + xn

2

)]Problem

Find the approximate value of ln 2 =∫ 21

dxx

using only the values of f (x) = 1x at

1, 65 , 7

5 , 85 , 9

5 , 2.

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 7 / 14

Page 23: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsRegular Partition Approximations Error Estimates

Rectangle Rules

Rectangle Rule for Approximating∫ ba f (x) dx

Left-endpoint rule:

Ln =b − a

n[f (x0) + f (x1) + · · ·+ f (xn−1)]

Right-endpoint rule:

Rn =b − a

n[f (x1) + f (x2) + · · ·+ f (xn)]

Midpoint rule:

Mn =b − a

n

[f

(x0 + x1

2

)+ · · ·+ f

(xn−1 + xn

2

)]Problem

Find the approximate value of ln 2 =∫ 21

dxx

using only the values of f (x) = 1x at

1, 65 , 7

5 , 85 , 9

5 , 2.

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 7 / 14

Page 24: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsRegular Partition Approximations Error Estimates

Rectangle Rules

Rectangle Rule for Approximating∫ ba f (x) dx

Left-endpoint rule:

Ln =b − a

n[f (x0) + f (x1) + · · ·+ f (xn−1)]

Right-endpoint rule:

Rn =b − a

n[f (x1) + f (x2) + · · ·+ f (xn)]

Midpoint rule:

Mn =b − a

n

[f

(x0 + x1

2

)+ · · ·+ f

(xn−1 + xn

2

)]Problem

Find the approximate value of ln 2 =∫ 21

dxx

using only the values of f (x) = 1x at

1, 65 , 7

5 , 85 , 9

5 , 2.

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 7 / 14

Page 25: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsRegular Partition Approximations Error Estimates

Rectangle Rules

Rectangle Rule for Approximating∫ ba f (x) dx

Left-endpoint rule:

Ln =b − a

n[f (x0) + f (x1) + · · ·+ f (xn−1)]

Right-endpoint rule:

Rn =b − a

n[f (x1) + f (x2) + · · ·+ f (xn)]

Midpoint rule:

Mn =b − a

n

[f

(x0 + x1

2

)+ · · ·+ f

(xn−1 + xn

2

)]Problem

Find the approximate value of ln 2 =∫ 21

dxx

using only the values of f (x) = 1x at

1, 65 , 7

5 , 85 , 9

5 , 2.

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 7 / 14

Page 26: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsRegular Partition Approximations Error Estimates

Rectangle Rules

Rectangle Rule for Approximating∫ ba f (x) dx

Left-endpoint rule:

Ln =b − a

n[f (x0) + f (x1) + · · ·+ f (xn−1)]

Right-endpoint rule:

Rn =b − a

n[f (x1) + f (x2) + · · ·+ f (xn)]

Midpoint rule:

Mn =b − a

n

[f

(x0 + x1

2

)+ · · ·+ f

(xn−1 + xn

2

)]Problem

Find the approximate value of ln 2 =∫ 21

dxx

using only the values of f (x) = 1x at

1, 65 , 7

5 , 85 , 9

5 , 2.

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 7 / 14

Page 27: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsRegular Partition Approximations Error Estimates

Rectangle Rules

Rectangle Rule for Approximating∫ ba f (x) dx

Left-endpoint rule:

Ln =b − a

n[f (x0) + f (x1) + · · ·+ f (xn−1)]

Right-endpoint rule:

Rn =b − a

n[f (x1) + f (x2) + · · ·+ f (xn)]

Midpoint rule:

Mn =b − a

n

[f

(x0 + x1

2

)+ · · ·+ f

(xn−1 + xn

2

)]Approximating ln 2 = 0.69314718 · · ·

L5 = 15

(1 + 5

6 + 57 + 5

8 + 59

)≈ 0.7456

R5 = 15

(56 + 5

7 + 58 + 5

9 + 12

)≈ 0.6456

M5 = 15

(1011 + 10

13 + 1015 + 10

17 + 1019

)≈ 0.6919

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 7 / 14

Page 28: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsRegular Partition Approximations Error Estimates

Rectangle Rules

Rectangle Rule for Approximating∫ ba f (x) dx

Left-endpoint rule:

Ln =b − a

n[f (x0) + f (x1) + · · ·+ f (xn−1)]

Right-endpoint rule:

Rn =b − a

n[f (x1) + f (x2) + · · ·+ f (xn)]

Midpoint rule:

Mn =b − a

n

[f

(x0 + x1

2

)+ · · ·+ f

(xn−1 + xn

2

)]Approximating ln 2 = 0.69314718 · · ·

L5 = 15

(1 + 5

6 + 57 + 5

8 + 59

)≈ 0.7456

R5 = 15

(56 + 5

7 + 58 + 5

9 + 12

)≈ 0.6456

M5 = 15

(1011 + 10

13 + 1015 + 10

17 + 1019

)≈ 0.6919

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 7 / 14

Page 29: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsRegular Partition Approximations Error Estimates

Rectangle Rules

Rectangle Rule for Approximating∫ ba f (x) dx

Left-endpoint rule:

Ln =b − a

n[f (x0) + f (x1) + · · ·+ f (xn−1)]

Right-endpoint rule:

Rn =b − a

n[f (x1) + f (x2) + · · ·+ f (xn)]

Midpoint rule:

Mn =b − a

n

[f

(x0 + x1

2

)+ · · ·+ f

(xn−1 + xn

2

)]Approximating ln 2 = 0.69314718 · · ·

L5 = 15

(1 + 5

6 + 57 + 5

8 + 59

)≈ 0.7456

R5 = 15

(56 + 5

7 + 58 + 5

9 + 12

)≈ 0.6456

M5 = 15

(1011 + 10

13 + 1015 + 10

17 + 1019

)≈ 0.6919

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 7 / 14

Page 30: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsRegular Partition Approximations Error Estimates

Rectangle Rules

Rectangle Rule for Approximating∫ ba f (x) dx

Left-endpoint rule:

Ln =b − a

n[f (x0) + f (x1) + · · ·+ f (xn−1)]

Right-endpoint rule:

Rn =b − a

n[f (x1) + f (x2) + · · ·+ f (xn)]

Midpoint rule:

Mn =b − a

n

[f

(x0 + x1

2

)+ · · ·+ f

(xn−1 + xn

2

)]Approximating ln 2 = 0.69314718 · · ·

L5 = 15

(1 + 5

6 + 57 + 5

8 + 59

)≈ 0.7456

R5 = 15

(56 + 5

7 + 58 + 5

9 + 12

)≈ 0.6456

M5 = 15

(1011 + 10

13 + 1015 + 10

17 + 1019

)≈ 0.6919

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 7 / 14

Page 31: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsRegular Partition Approximations Error Estimates

Error Estimates

∣∣∣∣∫ b

af (x) dx − Ln

∣∣∣∣ ≤ (b − a

n

)[f (b)−f (a)]

Error Estimates

Left-endpoint rule:

ELn =

∫ b

af (x) dx − Ln =

1

2

(b − a)2

nf ′(c) = O(∆x)

Right-endpoint rule:

ERn =

∫ b

af (x) dx − Rn =

1

2

(b − a)2

nf ′(c) = O(∆x)

Midpoint rule:

EMn =

∫ b

af (x) dx −Mn =

1

24

(b − a)3

n2f ′′(c) = O((∆x)2)

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 8 / 14

Page 32: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsRegular Partition Approximations Error Estimates

Error Estimates

∣∣∣∣∫ b

af (x) dx − Ln

∣∣∣∣ ≤ (b − a

n

)[f (b)−f (a)]

Error Estimates

Left-endpoint rule:

ELn =

∫ b

af (x) dx − Ln =

1

2

(b − a)2

nf ′(c) = O(∆x)

Right-endpoint rule:

ERn =

∫ b

af (x) dx − Rn =

1

2

(b − a)2

nf ′(c) = O(∆x)

Midpoint rule:

EMn =

∫ b

af (x) dx −Mn =

1

24

(b − a)3

n2f ′′(c) = O((∆x)2)

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 8 / 14

Page 33: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsRegular Partition Approximations Error Estimates

Error Estimates

∣∣∣∣∫ b

af (x) dx − Ln

∣∣∣∣ ≤ (b − a

n

)[f (b)−f (a)]

Error Estimates

Left-endpoint rule:

ELn =

∫ b

af (x) dx − Ln =

1

2

(b − a)2

nf ′(c) = O(∆x)

Right-endpoint rule:

ERn =

∫ b

af (x) dx − Rn =

1

2

(b − a)2

nf ′(c) = O(∆x)

Midpoint rule:

EMn =

∫ b

af (x) dx −Mn =

1

24

(b − a)3

n2f ′′(c) = O((∆x)2)

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 8 / 14

Page 34: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsRegular Partition Approximations Error Estimates

Error Estimates

∣∣∣∣∫ b

af (x) dx − Ln

∣∣∣∣ ≤ (b − a

n

)[f (b)−f (a)]

Error Estimates

Left-endpoint rule:

ELn =

∫ b

af (x) dx − Ln =

1

2

(b − a)2

nf ′(c) = O(∆x)

Right-endpoint rule:

ERn =

∫ b

af (x) dx − Rn =

1

2

(b − a)2

nf ′(c) = O(∆x)

Midpoint rule:

EMn =

∫ b

af (x) dx −Mn =

1

24

(b − a)3

n2f ′′(c) = O((∆x)2)

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 8 / 14

Page 35: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsRegular Partition Approximations Error Estimates

Error Estimates: Example

Error Estimates

Left-endpoint rule:

ELn =

∫ b

af (x) dx − Ln =

1

2

(b − a)2

nf ′(c) = O(∆x)

Right-endpoint rule:

ERn =

∫ b

af (x) dx − Rn =

1

2

(b − a)2

nf ′(c) = O(∆x)

Midpoint rule:

EMn =

∫ b

af (x) dx −Mn =

1

24

(b − a)3

n2f ′′(c) = O((∆x)2)

Approximating ln 2 = 0.69314718 · · ·Note that f (x) = 1

x , f ′(x) = − 1x2 , f ′′(x) = 2

x3 .

|ELn | = |ER

n | ≤ 12

(2−1)2

5 maxc∈[1,2] |f ′(c)| = 110

|EMn | ≤ 1

24(2−1)3

52 maxc∈[1,2] |f ′′(c)| = 1300

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 9 / 14

Page 36: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsRegular Partition Approximations Error Estimates

Error Estimates: Example

Error Estimates

Left-endpoint rule:

ELn =

∫ b

af (x) dx − Ln =

1

2

(b − a)2

nf ′(c) = O(∆x)

Right-endpoint rule:

ERn =

∫ b

af (x) dx − Rn =

1

2

(b − a)2

nf ′(c) = O(∆x)

Midpoint rule:

EMn =

∫ b

af (x) dx −Mn =

1

24

(b − a)3

n2f ′′(c) = O((∆x)2)

Approximating ln 2 = 0.69314718 · · ·Note that f (x) = 1

x , f ′(x) = − 1x2 , f ′′(x) = 2

x3 .

|ELn | = |ER

n | ≤ 12

(2−1)2

5 maxc∈[1,2] |f ′(c)| = 110

|EMn | ≤ 1

24(2−1)3

52 maxc∈[1,2] |f ′′(c)| = 1300

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 9 / 14

Page 37: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsRegular Partition Approximations Error Estimates

Error Estimates: Example

Error Estimates

Left-endpoint rule:

ELn =

∫ b

af (x) dx − Ln =

1

2

(b − a)2

nf ′(c) = O(∆x)

Right-endpoint rule:

ERn =

∫ b

af (x) dx − Rn =

1

2

(b − a)2

nf ′(c) = O(∆x)

Midpoint rule:

EMn =

∫ b

af (x) dx −Mn =

1

24

(b − a)3

n2f ′′(c) = O((∆x)2)

Approximating ln 2 = 0.69314718 · · ·Note that f (x) = 1

x , f ′(x) = − 1x2 , f ′′(x) = 2

x3 .

|ELn | = |ER

n | ≤ 12

(2−1)2

5 maxc∈[1,2] |f ′(c)| = 110

|EMn | ≤ 1

24(2−1)3

52 maxc∈[1,2] |f ′′(c)| = 1300

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 9 / 14

Page 38: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsApproximations Error Estimates

Trapeziodal and Parabolic Approximations

∫ xi

xi−1f (x) dx Trapeziodal Parabolic

Approximations of∫ xi

xi−1f (x) dx

12 [f (xi−1) + f (xi )]∆x , 1

6

[f (xi−1) + 4f

(xi−1+xi

2

)+ f (xi )

]∆x

trapeziodal Parabolic

Approximations of∫ ba f (x) dx =

∑ni=1

∫ xi

xi−1f (x) dx∑n

i=1∆x2 [f (xi−1) + f (xi )] ,

∑ni=1

∆x6

[f (xi−1) + 4f

(xi−1+xi

2

)+ f (xi )

]Trapeziodal Parabolic

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 10 / 14

Page 39: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsApproximations Error Estimates

Trapeziodal and Parabolic Approximations

∫ xi

xi−1f (x) dx Trapeziodal Parabolic

Approximations of∫ xi

xi−1f (x) dx

12 [f (xi−1) + f (xi )]∆x , 1

6

[f (xi−1) + 4f

(xi−1+xi

2

)+ f (xi )

]∆x

trapeziodal Parabolic

Approximations of∫ ba f (x) dx =

∑ni=1

∫ xi

xi−1f (x) dx∑n

i=1∆x2 [f (xi−1) + f (xi )] ,

∑ni=1

∆x6

[f (xi−1) + 4f

(xi−1+xi

2

)+ f (xi )

]Trapeziodal Parabolic

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 10 / 14

Page 40: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsApproximations Error Estimates

Trapeziodal and Parabolic Approximations

∫ xi

xi−1f (x) dx Trapeziodal Parabolic

Approximations of∫ xi

xi−1f (x) dx

12 [f (xi−1) + f (xi )]∆x , 1

6

[f (xi−1) + 4f

(xi−1+xi

2

)+ f (xi )

]∆x

trapeziodal Parabolic

Approximations of∫ ba f (x) dx =

∑ni=1

∫ xi

xi−1f (x) dx∑n

i=1∆x2 [f (xi−1) + f (xi )] ,

∑ni=1

∆x6

[f (xi−1) + 4f

(xi−1+xi

2

)+ f (xi )

]Trapeziodal Parabolic

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 10 / 14

Page 41: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsApproximations Error Estimates

Trapeziodal and Parabolic Approximations

∫ xi

xi−1f (x) dx Trapeziodal Parabolic

Approximations of∫ xi

xi−1f (x) dx

12 [f (xi−1) + f (xi )]∆x , 1

6

[f (xi−1) + 4f

(xi−1+xi

2

)+ f (xi )

]∆x

trapeziodal Parabolic

Approximations of∫ ba f (x) dx =

∑ni=1

∫ xi

xi−1f (x) dx∑n

i=1∆x2 [f (xi−1) + f (xi )] ,

∑ni=1

∆x6

[f (xi−1) + 4f

(xi−1+xi

2

)+ f (xi )

]Trapeziodal Parabolic

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 10 / 14

Page 42: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsApproximations Error Estimates

Trapeziodal and Parabolic Approximations

∫ xi

xi−1f (x) dx Trapeziodal Parabolic

Approximations of∫ xi

xi−1f (x) dx

12 [f (xi−1) + f (xi )]∆x , 1

6

[f (xi−1) + 4f

(xi−1+xi

2

)+ f (xi )

]∆x

trapeziodal Parabolic

Approximations of∫ ba f (x) dx =

∑ni=1

∫ xi

xi−1f (x) dx∑n

i=1∆x2 [f (xi−1) + f (xi )] ,

∑ni=1

∆x6

[f (xi−1) + 4f

(xi−1+xi

2

)+ f (xi )

]Trapeziodal Parabolic

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 10 / 14

Page 43: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsApproximations Error Estimates

Trapeziodal and Parabolic Approximations

∫ xi

xi−1f (x) dx Trapeziodal Parabolic

Approximations of∫ xi

xi−1f (x) dx

12 [f (xi−1) + f (xi )]∆x , 1

6

[f (xi−1) + 4f

(xi−1+xi

2

)+ f (xi )

]∆x

trapeziodal Parabolic

Approximations of∫ ba f (x) dx =

∑ni=1

∫ xi

xi−1f (x) dx∑n

i=1∆x2 [f (xi−1) + f (xi )] ,

∑ni=1

∆x6

[f (xi−1) + 4f

(xi−1+xi

2

)+ f (xi )

]Trapeziodal Parabolic

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 10 / 14

Page 44: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsApproximations Error Estimates

Trapeziodal and Simpson’s Rules

Trapeziodal and Simpson’s Rules for Approximating∫ ba f (x) dx

Trapeziodal Rule:

Tn =b − a

2n[f (x0) + 2f (x1) + · · ·+ 2f (xn−1) + f (xn)]

Simpson’s Rule (Parabolic):

Sn =b − a

6n

f (x0) + f (xn) + 2

[f (x1) + · · ·+ 2f (xn−1)

]+4

[f

(x0 + x1

2

)+ · · ·+ f

(xn−1 + xn

2

)]Problem

Find the approximate value of ln 2 =∫ 21

dxx

using only the values of f (x) = 1x at

1, 65 , 7

5 , 85 , 9

5 , 2.

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 11 / 14

Page 45: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsApproximations Error Estimates

Trapeziodal and Simpson’s Rules

Trapeziodal and Simpson’s Rules for Approximating∫ ba f (x) dx

Trapeziodal Rule:

Tn =b − a

2n[f (x0) + 2f (x1) + · · ·+ 2f (xn−1) + f (xn)]

Simpson’s Rule (Parabolic):

Sn =b − a

6n

f (x0) + f (xn) + 2

[f (x1) + · · ·+ 2f (xn−1)

]+4

[f

(x0 + x1

2

)+ · · ·+ f

(xn−1 + xn

2

)]Problem

Find the approximate value of ln 2 =∫ 21

dxx

using only the values of f (x) = 1x at

1, 65 , 7

5 , 85 , 9

5 , 2.

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 11 / 14

Page 46: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsApproximations Error Estimates

Trapeziodal and Simpson’s Rules

Trapeziodal and Simpson’s Rules for Approximating∫ ba f (x) dx

Trapeziodal Rule:

Tn =b − a

2n[f (x0) + 2f (x1) + · · ·+ 2f (xn−1) + f (xn)]

Simpson’s Rule (Parabolic):

Sn =b − a

6n

f (x0) + f (xn) + 2

[f (x1) + · · ·+ 2f (xn−1)

]+4

[f

(x0 + x1

2

)+ · · ·+ f

(xn−1 + xn

2

)]Problem

Find the approximate value of ln 2 =∫ 21

dxx

using only the values of f (x) = 1x at

1, 65 , 7

5 , 85 , 9

5 , 2.

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 11 / 14

Page 47: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsApproximations Error Estimates

Trapeziodal and Simpson’s Rules

Trapeziodal and Simpson’s Rules for Approximating∫ ba f (x) dx

Trapeziodal Rule:

Tn =b − a

2n[f (x0) + 2f (x1) + · · ·+ 2f (xn−1) + f (xn)]

Simpson’s Rule (Parabolic):

Sn =b − a

6n

f (x0) + f (xn) + 2

[f (x1) + · · ·+ 2f (xn−1)

]+4

[f

(x0 + x1

2

)+ · · ·+ f

(xn−1 + xn

2

)]Problem

Find the approximate value of ln 2 =∫ 21

dxx

using only the values of f (x) = 1x at

1, 65 , 7

5 , 85 , 9

5 , 2.

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 11 / 14

Page 48: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsApproximations Error Estimates

Trapeziodal and Simpson’s Rules

Trapeziodal and Simpson’s Rules for Approximating∫ ba f (x) dx

Trapeziodal Rule:

Tn =b − a

2n[f (x0) + 2f (x1) + · · ·+ 2f (xn−1) + f (xn)]

Simpson’s Rule (Parabolic):

Sn =b − a

6n

f (x0) + f (xn) + 2

[f (x1) + · · ·+ 2f (xn−1)

]+4

[f

(x0 + x1

2

)+ · · ·+ f

(xn−1 + xn

2

)]Approximating ln 2 = 0.69314718 · · ·

T5 = 110

(1 + 10

6 + 107 + 10

8 + 109 + 1

2

)≈ 0.6956

S5 = 130

1 + 1

2 + 2(

56 + 5

7 + 58 + 5

9

)+4

[1011 + 10

13 + 1015 + 10

17 + 1019

]≈ 0.6932

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 11 / 14

Page 49: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsApproximations Error Estimates

Trapeziodal and Simpson’s Rules

Trapeziodal and Simpson’s Rules for Approximating∫ ba f (x) dx

Trapeziodal Rule:

Tn =b − a

2n[f (x0) + 2f (x1) + · · ·+ 2f (xn−1) + f (xn)]

Simpson’s Rule (Parabolic):

Sn =b − a

6n

f (x0) + f (xn) + 2

[f (x1) + · · ·+ 2f (xn−1)

]+4

[f

(x0 + x1

2

)+ · · ·+ f

(xn−1 + xn

2

)]Approximating ln 2 = 0.69314718 · · ·

T5 = 110

(1 + 10

6 + 107 + 10

8 + 109 + 1

2

)≈ 0.6956

S5 = 130

1 + 1

2 + 2(

56 + 5

7 + 58 + 5

9

)+4

[1011 + 10

13 + 1015 + 10

17 + 1019

]≈ 0.6932

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 11 / 14

Page 50: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsApproximations Error Estimates

Trapeziodal and Simpson’s Rules

Trapeziodal and Simpson’s Rules for Approximating∫ ba f (x) dx

Trapeziodal Rule:

Tn =b − a

2n[f (x0) + 2f (x1) + · · ·+ 2f (xn−1) + f (xn)]

Simpson’s Rule (Parabolic):

Sn =b − a

6n

f (x0) + f (xn) + 2

[f (x1) + · · ·+ 2f (xn−1)

]+4

[f

(x0 + x1

2

)+ · · ·+ f

(xn−1 + xn

2

)]Approximating ln 2 = 0.69314718 · · ·

T5 = 110

(1 + 10

6 + 107 + 10

8 + 109 + 1

2

)≈ 0.6956

S5 = 130

1 + 1

2 + 2(

56 + 5

7 + 58 + 5

9

)+4

[1011 + 10

13 + 1015 + 10

17 + 1019

]≈ 0.6932

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 11 / 14

Page 51: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsApproximations Error Estimates

Error Estimates

∣∣∣∣∫ b

af (x) dx − Tn

∣∣∣∣ ≤ 1

2

(b − a

n

)[f (b)−f (a)]

Error Estimates

Trapeziodal Rule:

ETn =

∫ b

af (x) dx − Tn = − 1

12

(b − a)3

n2f ′′(c) = O((∆x)2)

Simpson’s Rule:

ESn =

∫ b

af (x) dx − Sn = − 1

2880

(b − a)5

n4f (4)(c) = O((∆x)4)

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 12 / 14

Page 52: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsApproximations Error Estimates

Error Estimates

∣∣∣∣∫ b

af (x) dx − Tn

∣∣∣∣ ≤ 1

2

(b − a

n

)[f (b)−f (a)]

Error Estimates

Trapeziodal Rule:

ETn =

∫ b

af (x) dx − Tn = − 1

12

(b − a)3

n2f ′′(c) = O((∆x)2)

Simpson’s Rule:

ESn =

∫ b

af (x) dx − Sn = − 1

2880

(b − a)5

n4f (4)(c) = O((∆x)4)

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 12 / 14

Page 53: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsApproximations Error Estimates

Error Estimates

∣∣∣∣∫ b

af (x) dx − Tn

∣∣∣∣ ≤ 1

2

(b − a

n

)[f (b)−f (a)]

Error Estimates

Trapeziodal Rule:

ETn =

∫ b

af (x) dx − Tn = − 1

12

(b − a)3

n2f ′′(c) = O((∆x)2)

Simpson’s Rule:

ESn =

∫ b

af (x) dx − Sn = − 1

2880

(b − a)5

n4f (4)(c) = O((∆x)4)

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 12 / 14

Page 54: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsApproximations Error Estimates

Error Estimates: Example

Error Estimates

Trapeziodal Rule:

ETn =

∫ b

af (x) dx − Tn = − 1

12

(b − a)3

n2f ′′(c) = O((∆x)2)

Simpson’s Rule:

ESn =

∫ b

af (x) dx − Sn = − 1

2880

(b − a)5

n4f (4)(c) = O((∆x)4)

Approximating ln 2 = 0.69314718 · · ·Note that f (x) = 1

x , f ′(x) = − 1x2 , f ′′(x) = 2

x3 ,

f (3)(x) = − 6x4 , f (4)(x) = 24

x5 .

|ETn | ≤ 1

12(2−1)3

52 maxc∈[1,2] |f ′′(c)| = 1150

|EMn | ≤ 1

2880(2−1)5

54 maxc∈[1,2] |f (4)(c)| = · · ·

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 13 / 14

Page 55: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsApproximations Error Estimates

Error Estimates: Example

Error Estimates

Trapeziodal Rule:

ETn =

∫ b

af (x) dx − Tn = − 1

12

(b − a)3

n2f ′′(c) = O((∆x)2)

Simpson’s Rule:

ESn =

∫ b

af (x) dx − Sn = − 1

2880

(b − a)5

n4f (4)(c) = O((∆x)4)

Approximating ln 2 = 0.69314718 · · ·Note that f (x) = 1

x , f ′(x) = − 1x2 , f ′′(x) = 2

x3 ,

f (3)(x) = − 6x4 , f (4)(x) = 24

x5 .

|ETn | ≤ 1

12(2−1)3

52 maxc∈[1,2] |f ′′(c)| = 1150

|EMn | ≤ 1

2880(2−1)5

54 maxc∈[1,2] |f (4)(c)| = · · ·

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 13 / 14

Page 56: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsApproximations Error Estimates

Error Estimates: Example

Error Estimates

Trapeziodal Rule:

ETn =

∫ b

af (x) dx − Tn = − 1

12

(b − a)3

n2f ′′(c) = O((∆x)2)

Simpson’s Rule:

ESn =

∫ b

af (x) dx − Sn = − 1

2880

(b − a)5

n4f (4)(c) = O((∆x)4)

Approximating ln 2 = 0.69314718 · · ·Note that f (x) = 1

x , f ′(x) = − 1x2 , f ′′(x) = 2

x3 ,

f (3)(x) = − 6x4 , f (4)(x) = 24

x5 .

|ETn | ≤ 1

12(2−1)3

52 maxc∈[1,2] |f ′′(c)| = 1150

|EMn | ≤ 1

2880(2−1)5

54 maxc∈[1,2] |f (4)(c)| = · · ·

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 13 / 14

Page 57: Lecture 11 - Section 8.7 Numerical Integrationjiwenhe/Math1432/lectures/lecture11.pdf · Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008

Riemann Sums Rectangle Approximations Trapeziodal and Parabolic ApproximationsApproximations Error Estimates

Outline

Riemann SumsArea ProblemLower and Upper SumsRiemann Sum

Rectangle ApproximationsRegular PartitionApproximationsError Estimates

Trapeziodal and Parabolic ApproximationsApproximationsError Estimates

Jiwen He, University of Houston Math 1432 – Section 26626, Lecture 11 February 19, 2008 14 / 14