The surface area of a sphere :
[tex]A=4 \pi r^2[/tex]
Solving this equation for r:
A/(4* pi) = r^2 apply sqrt to both sides:
r = sqrt [A/(4 pi)]
Then the radius of a sphere as a function of its surface area :
[tex]r= \sqrt{ \frac{A}{4 \pi } } [/tex]
Hope you got the idea
