Question

How do you find the surface area of a sphere? What should the label be?

Answer 1

Surface area = 4 pi r^2

where 

pi : 3.14 a constant

r : raduis

surface area is the change of volume with respect to raduis

volume = 4/3 pi r^3

dvolume/dr = 4 pi r^2 

you can prove the identity with double integration in spherical coordinates or volumes of revolutions and polar coordinates