Geo.4.11.17.sec.12.1.notebook
Chapter 12
April 11, 2017
p.587
Chords, Secants, and Tangents
12-1 Circles in the coordinate plane
Objective: Write the equation of a circle.
Warm Up
Use the distance formula to find the
length of AB with A (2, 4) and B (1, - 1).
Geo.4.11.17.sec.12.1.notebook
April 11, 2017
Consider the equation: x2 + y2 = 25
y
x
0
0
0
0
4
4
4
4
You can use the Distance Formula to find an equation of a circle with center (h, k) and radius r. Let (x, y) be any point on the circle. The radius is the distance from (h, k) to (x, y).
Geo.4.11.17.sec.12.1.notebook
April 11, 2017
THEOREM 12-1
Equation of a Circle
The standard form of the equation of a circle
with center (h, k) and radius r is:
r2 = (x - h)2 + (y - k)2
Find the center and radius of each circle.
100 = (x - 2)2 + (y - 3)2
center
radius =
64 = (x - 7)2 + (y + 2)2
center
radius =
Geo.4.11.17.sec.12.1.notebook
April 11, 2017
Write the equation of each circle:
Center ( - 2, - 1), r = √2
Center (3, 5), r = 6
Center (0, 0), r = 5
What is the equation
of this circle?
Geo.4.11.17.sec.12.1.notebook
What is the equation
of this circle?
9 = (x + 3)2 + (y - 1)2
April 11, 2017
Geo.4.11.17.sec.12.1.notebook
HW # 86
Equations of Circles Worksheets
April 11, 2017