S= 2pier^2 + 2pierh , solve for h
\(2pier^2+2pierh=S\ \ \ |subtract\ 2pier^2\ from\ both\ sides\\\\2pierh=S-2pier^2\ \ \ \ |divide\ both\ sides\ by\ 2pier\\\\\boxed{h=\dfrac{S-2pier^2}{2pier}\ other\ form\ h=\dfrac{S}{2pier}-r}\)
