sec 7.4: integration of rational functions by partial fractions example find example find example...
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Sec 7.4: INTEGRATION OF RATIONAL FUNCTIONS BY PARTIAL FRACTIONS
Example
Find dxx
1
Example
Find dx
x
1
1
Example
Find dx
ax
1
Example
Find dx
x
x
3
2Example
Find
dxx
xx
3
42
Rational function:)(
)()(xq
xpxf
2
1
2
1
xx 4
42 x
2
1
2
1
xx4
42 x
dx
xx 2
1
2
1dx
x 4
42
Sec 7.4: INTEGRATION OF RATIONAL FUNCTIONS BY PARTIAL FRACTIONS
Sec 7.4: INTEGRATION OF RATIONAL FUNCTIONS BY PARTIAL FRACTIONS
)deg()deg( if qp dxxq
xp )(
)(Use long division1
)32)(1()( xxxq
Factor q(x) as linear factors or irreducible quadratic 3)3)(4()( 2 xxxq
5
1
2
12
x
x
x
Express p(x)/q(x) as a sum of partial fraction4ii cbxax
BAx
bax
A
)(or
)( 2
q(x)= product of linear factor
All distinct Some repeated
q(x)= product of quadratic (irred)
All distinct repeatedcase1
case2 case3 case4
Check if we can use subsitution2 15
522
xx
x
Sec 7.4: INTEGRATION OF RATIONAL FUNCTIONS BY PARTIAL FRACTIONS
Example Find
dxxxx
xx
232
1223
2
Example
Find dx
x
4
12
q(x)= product of linear factor
All distinct Some repeated
case1case2
Sec 7.4: INTEGRATION OF RATIONAL FUNCTIONS BY PARTIAL FRACTIONS
Example
Find dx
xxx
xxx
1
14223
24
Example
32 )1(
1
xx
x
q(x)= product of linear factor
All distinct Some repeated
case1case2
322 )1()1(1
x
E
x
D
x
C
x
B
x
A
Sec 7.4: INTEGRATION OF RATIONAL FUNCTIONS BY PARTIAL FRACTIONS
q(x)= product of quadratic (irred)
All distinct repeated
case3 case4
Example
)4)(1)(2( 22 xxx
x
412 22
x
EDx
x
CBx
x
A
Example
Find dx
xx
xx
4
423
2
Sec 7.4: INTEGRATION OF RATIONAL FUNCTIONS BY PARTIAL FRACTIONS
q(x)= product of quadratic (irred)
All distinct repeated
case3 case4
Example
222 )4)(1( xx
x
)4(41 222
x
FEx
x
DCx
x
BAx
Example
Express only
dxxxxxx
xx
)1)(1)(1(
1322
23
Example
Find
dxxx
xxx
)1(
2122
32
Sec 7.4: INTEGRATION OF RATIONAL FUNCTIONS BY PARTIAL FRACTIONS
RATIONALIZING SUBSTITUTIONS
Some nonrational functions can be changed into rational functions
n xg )(contains )(xf
Example
Find
dxx
x
4
n xgu )( :use
Sec 7.4: INTEGRATION OF RATIONAL FUNCTIONS BY PARTIAL FRACTIONS
rational function of sin and cos
2
2
1
1cos
t
tx
Use the following to convert it into rational function121
2sin
t
tx
dt
tdx
21
2
xt x )
2tan(
Evaluate the integral then use:2