Question 542460
The center of the circle will be the midpoint of the line segment representing the diameter
Given the two endpoints (-3,2) and (5,-6) the midpoint has coordinates 
x = (-3+5)/2 = 1
y = (2-6)/2 = -2
The radius is the distance between the center and one of the endpoints:
r = sqrt((1 - -3)^2 + (-2 - 2)^2) = sqrt(16 + 16) = sqrt(32) = 4*{{{sqrt(2)}}}