Question

Calculate the ROC, dA/dD, where A is the surface area of a sphere of diameter D (the surface area of a sphere of radius r is 4pir^2)

I've tried 8pir, and it was incorrect, any ideas?

Answer 1

r=D/2
A(D)=4(pi)r^2=4(pi)(D/2)^2=(pi)D^2
dA/dD=2(pi)D

Answer 2

Thank you very much, that worked!