Points $A(-1, -2)$ and $B(3, 2)$ are the endpoints of a diameter of a circle graphed in a coordinate plane. How many square units are in the area of the circle? Express your answer in terms of $\pi$.
Find the distance between A and B
sqrt [ ( 3 - - 1)^2 + ( 2 - - 2)^2 ] = sqrt [ 4^2 + 4^2 ] = sqrt (32)
Take 1/2 of this = sqrt (32) / 2 = the radius of the circle
Area = pi (sqrt (32) / 2 ) ^2 = pi (32 / 4) = 8 pi units^2
