The area of a circle as a function of radius is A(r) = r2, with area measured

Question:

The area of a circle as a function of radius is A(r) = πr2, with area measured in cm2 and radius measured in centimeters. Find the derivative of area with respect to radius. On a geometric diagram, illustrate the area corresponding to ΔA = A(r + Δr) - A(r). What is a geometric interpretation of the derivative? Do the units make sense?
Find the derivatives of the above functions.