Big Ideas Math Geometry, 2014
BI
Big Ideas Math Geometry, 2014 View details
7. Circles in the Coordinate Plane
Continue to next subchapter

Exercise 5 Page 575

Use the Distance Formula.

(x-4)^2+(y+1)^2=9

Practice makes perfect
To find the equation of the circle we will use the Distance Formula. d = sqrt((x_2-x_1)^2 + (y_2-y_1)^2)In this form, the center of the circle is ( x_1, x_2) and d is the circle's radius. Let's label the radius r. r=sqrt((x_2- x_1)^2+(y_2- y_1)^2) We have been given that the circle has its center at ( 4, -1) and radius 3. Let's substitute these values into the formula and simplify.
r=sqrt((x_2- x_1)^2+(y_2- y_1)^2)
3=sqrt((x_2- 4)^2+(y_2-( - 1))^2)
â–Ľ
Simplify
3^2=(x_2-4)^2+(y_2-(- 1))^2
9=(x_2-4)^2+(y_2-(- 1))^2
9=(x_2-4)^2+(y_2+1)^2
(x_2-4)^2+(y_2+1)^2=9
The equation of the circle can be written as (x_2-4)^2+(y_2+1)^2=9.