Question

(50 points) A diameter of a circle has endpoints P(-10, -2) and Q(4,6)

A. Find the center of the circle

B. Find the radius. if your answer is not an integer, express it in radical form.

C. Write an equation for the circle

Answer 1

Explanation:

The center of the circle is the midpoint of the two end points of the diameter.

Formula

Center = (x2 + x1)/2 , (y2 + y1)/2

Givens

x2 = 4

x1 = - 10

y2 = 6

y1 = - 2

Solution

Center = (4 - 10)/2, (6 - 2)/2

Center = -6/2 , 4/2

Center = - 3 , 2

So far what you have is

(x+3)^2 + (y - 2)^2 = r^2

Now you have to find the radius.

You can use either of the endpoints to find the radius.

find the distance from (4,6) to (-3,2)

r^2 = ( (x2 - x1)^2 + (y2 - y1)^2 )

x2 = 4

x1 = -3

y2 = 6

y1 = 2

r^2 = ( (4 - -3)^2 + (6 - 2)^2 )

r^2 = ( (7)^2 + 4^2)

r^2 = ( 49 + 16)

r^2 = 65

Ultimate formula is

(x+3)^2 + (y - 2)^2 = 65

The radius is √65 = 8.06