The midpoint is simply the average of the x and y coordinates of two points.
p=((-1+4)/2, (5-3)/2)
p=(1.5, 1) so the midpoint, or center of the circle is (1.5, 1)
The distance between the two points, which can be found using an extension of the Pythagorean Theorem.
d^2=(x2-x1)^2+(y2-y1)^2, in this case:
d^2=(4--1)^2+(-3-5)^2
d^2=5^2+(-8)^2
d^2=25+64
d^2=89
d=√89, since d=2r
2r=√89
r=√(89/4)
r=√22.25
r≈4.7 units (to nearest tenth of a unit)
