algebra ii chapter 8: conic sections. cheat sheet in chapter 8 you are allowed a “cheat sheet”...
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Cheat Sheet• In chapter 8 you are allowed a “cheat sheet”
• You are to bring in a tissue box, that has not been opened, and cover it with paper.• You are allowed to write anything on this box that you so
choose.• You may use it on your quiz and chapter test.
• When we are done with Chapter 8, you must give the tissue box to me.
• It is your decision to do this, you may not have any other form a “cheat sheet”
8.1: Midpoint and Distance Formulas
• Find the midpoint of a segment on the coordinate plane
• Find the distance between two points on the coordinate plane
The Midpoint Formula
• The midpoint is the point in the middle of a segment• Definition: M is the midpoint of PQ if M is
between P and Q and PM = MQ.
• Formula:•
Example 1:
• Find the midpoint of each line segment with endpoints at the given coordinates:• (12, 7) and (-2, 11)
• (-8, -3) and (10, 9)
• (4, 15) and (10, 1)
• (-3, -3) and (3, 3)
“Curveball Problem” Example 2:
• Segment MN has a midpoint P. If M has coordinates (14, -3) and P has coordinates (-8, 6), what are the coordinates of N?
• Circle R has a diameter ST. If R has coordinates (-4, -8) and S has coordinates (1, 4), what are the coordinates of T?
“Curveball Problem” Example 2:
• Circle Q has a diameter AB. If A is at (-3,-5) and the center is at (2, 3), find the coordinates of the B.
The Distance Formula
• Distance is always a positive number
• You can find distance using the Pythagorean Theorem or using a formula derived from it
• Formula:•
Example 3:
• Find the distance between each pair of points with the given coordinates• (3, 7) and (-1, 4)
• (-2, -10) and (10, -5)
• (6, -6) and (-2, 0)
Example 4:
• Rectangle ABCD has vertices A(1, 4), B(3, 1), C(-3, -2), and D(-5, 1). Find the perimeter and area of ABCD
• Circle R has diameter ST with endpoints S(4, 5) and T(-2, -3). What are the circumference and are of the circle? (Round to two decimal places)
Summary:
• Learn the midpoint and distance formulas
• Be able to answer any question that may involve them.
• Questions?
Example 1:
• Write y = 3x2 + 24x + 50 in vertex form. Identify the vertex, axis of symmetry, and direction of opening of the parabola.
Example 1:
• Write y = -x2 – 2x + 3 in vertex form. Identify the vertex, axis of symmetry, and direction of opening of the parabola.
Graph Parabola
• You must always graph:• Vertex• Axis of Symmetry• Five points on the graph (this is to get
the shape)• Focus: point in which all points in a
parabola are equidistant• Directrix: line that the parabola will
never cross
Concept Summary (pg 422)Form of Equation y = a(x – h)2 + k x = a(y – k)2 + h
Vertex (h, k) (h, k)
Axis of Symmetry x = h y = k
Focus
Directrix
Direction of Opening
upward if a > 0downward if a < 0
right if a > 0left if a < 0
Example
Example 2:
• Identify the coordinates of the vertex and focus, the equations of the axis of symmetry and directrix, and the direction of opening of the parabola• y = x2 + 6x – 4
• x = y2 – 8y + 6
Example 2:
• Identify the coordinates of the vertex and focus, the equations of the axis of symmetry and directrix, and the direction of opening of the parabola• y = 8x – 2x2 + 10
• x = -y2 – 4y – 1
Classwork/Homework
• Workbook– Section 8.1
• 1, 3, 5, 11, 17, 19, 21, 31, 32
– Section 8.2• 1 – 6 (all)
Circle
• A circle is the set of all point in a plane that are equidistant from a given point in the plane, called the center.
• Equation of a circle:• (x – h)2 + (y – k)2 = r2
r = radius
center
(h, k)
Example One:
• Write an equation for the circle that satisfies each set of conditions:• Center (8, -3), Radius 6
• Center (5, -6), Radius 4
Example One:
• Write an equation for the circle that satisfies each set of conditions:• Center (-5, 2) passes through (-9, 6)
• Center (7, 7) passes through (12, 9)
Example One:
• Write an equation for the circle that satisfies each set of conditions:• Endpoints of a diameter are (-4, -2) and (8,
4)
• Endpoints of a diameter are (-4, 3) and (6, -8)
Graph circles
• Make sure the equation is in standard form
• Graph the center
• Use the length of the radius to graph four points on the circle (up, down, left, right)
• Connect the dots to create the circle
Example Two:• Find the center and radius of the
circle given the equation. Then graph the circle• (x – 3)2 + y2 = 9
Example Two:• Find the center and radius of the
circle given the equation. Then graph the circle• (x – 1)2 + (y + 3)2 = 25
Example Two:• Find the center and radius of the circle
given the equation. Then graph the circle• x2 + y2 – 10x + 8y + 16 = 0
Example Two:• Find the center and radius of the circle
given the equation. Then graph the circle• x2 + y2 – 4x + 6y = 12
Homework Answers: Workbook 8.3
1. (x + 4)2 + (y – 2)2 = 642. x2 + y2 = 163. (x + ¼)2 + (y + )2 = 504. (x – 2.5)2 + (y – 4.2)2 = 0.815. (x + 1)2 + (y + 7)2 = 56. (x + 9)2 + (y + 12)2 = 747. (x + 6)2 + (y – 5)2 = 258. (-3, 0); r = 49. (0, 0); r = 210. (-1, -3); r = 611. (1, -2); r = 412. (3, 0); r = 313. (-1, -3); r = 3
3
Ellipse• An ellipse is like an oval.
• Every ellipse has two axes of symmetry• Called the major axis and the minor axis
• The axes intersect at the center of the ellipse• The major axis is bigger than the minor axis• We use c2 = a2 – b2 to find c
• a is always greater b
• The equation is always equal to 1
Ellipses Chart (pg 434)
Standard Form of Equation
Center (h,k) (h,k)
Direction of Major Axis
Horizontal Vertical
Foci (h + c, k), (h – c, k)
(h, k + c), (h, k – c)
Length of Major Axis
2a units 2a units
Length of Minor Axis
2b units 2b units
2 2
2 2
x - h y - k+ =1
a b
2 2
2 2
y - k x - h+ =1
a b
Standard Form
Find the coordinates of the center and foci and the lengths of the major and minor axes of the ellipse with equation: x2 + 4y2 + 24y = -32
Standard Form
Find the coordinates of the center and foci and the lengths of the major and minor axes of the ellipse with equation: 9x2 + 6y2 – 36x + 12y = 12
Hyperbolas Chart
Standard Form of Equation
Direction of Transverse Axis
Horizontal Vertical
Foci (h + c, 0), (h - c, 0)
(0, h + c), (0, h - c)
Vertices (h + a, 0), (h - a, 0)
(0, h + a), (0, h - a)
Length of Transverse Axis
2a units 2a units
Length of Conjugate Axis
2b units 2b units
Equations of Asymptotes
2 2
2 2
x - h y - k- =1
a b
2 2
2 2
y - k x - h- =1
a b
by - k = ± (x - h)
aa
y - k = ± (x - h)b
Standard Form:
Find the coordinates of the vertices and foci and the equations of the asymptotes for the hyperbola with equation
4x2 – 9y2 – 32x – 18y + 19 = 0
Standard Form:
Find the coordinates of the vertices and foci and the equations of the asymptotes for the hyperbola with equation
x2 – y2 + 6x + 10y – 17 = 0
8.6 Conic Sections
The equation of any conic section can be written in the general quadratic equation:
Ax2 + Bxy + Cy2 + Dx + Ey + F = 0where A, B, and C ≠ 0
If you are given an equation in this general form, you can complete the square to write the equation in one of the standard forms you have already learned.
Standard Forms (you already know )
Conic Section
Standard Form of Equation
Parabola y = a(x – h)2 + k x = a(y – k)2 + h
Circle (x – h)2 + (y – k)2 = r2
Ellipse
Hyperbola
2 2
2 2
x - h y - k+ =1
a b
2 2
2 2
y - k x - h+ =1
a b
2 2
2 2
x - h y - k- =1
a b 2 2
2 2
y - k x - h- =1
a b
Identifying Conic Sections
Relationship of A and C Type of Conic Section
Only x2 or y2 Parabola
Same number in front of x2 and y2
Circle
Different number in front of x2 and y2 with plus sign
Ellipse
Different number in front of x2 and y2 with plus sign or minus sign
Hyperbola
Example One:
Write each equation in standard form. Then state whether the graph of the equation is a parabola, circle, ellipse, and hyperbola.y = x2 + 4x + 1
x2 + y2 = 4x + 2
y2 – 2x2 – 16 = 0
x2 + 4y2 + 2x – 24y + 33 = 0
Example Two:
Without writing the equation in standard form, state whether the graph of each equation is a parabola, circle, ellipse, and hyperbola.x2 + 2y2 + 6x – 20y + 53 = 0
x2 + y2 – 4x – 14y + 29 = 0
3y2 + x – 24y + 46 = 0
6x2 – 5y2 + 24x + 20y – 56 = 0
Your Turn:
Without writing the equation in standard form, state whether the graph of each equation is a parabola, circle, ellipse, and hyperbola.x2 + y2 – 6x + 4y + 3 = 0
6x2 – 60x – y + 161 = 0
x2 – 4y2 – 16x + 24y – 36 = 0
x2 + 2y2 + 8x + 4y + 2 = 0