Answer:
2.5
Step-by-step explanation:
First find the length of RS
x2 = 4
x1 = - 1
y2 = 2
y1 = 2
RS^2 = (2 - 2)^2 + (4 - -1 ) ^2
RS^2 = 0 + 5^2
RS = sqrt(5^2)
RS = 5
That is the length of the diameter. The radius is 1/2 that
r = d/2
d = 5
r = 5/2
r = 2.5
