Finding Derivatives with a Constant Radius

[myria36]

Homework Statement

the total surface area of a right circular cylinder is given by the formula: (A = 2Pir(r + h) ).
where r is the radius and h is the height.
sub part a) find the rate of change of A with respect to h is r remains constant

i know how to take derivatives. the only thing is that in this case, I am not sure how to take the derivative of h since it is only present in one term.

Homework Equations

the derivative equation

The Attempt at a Solution

i first ditributed the 2pir, to yield
2pir^2 + 2pirh
2pir^2(h/h) + 2pirh
h (2pir^2 h^-1 + 2pi r)
now i am stuck here. i can't take the derivative of all the h's in my problem, because one h is still present in the equation.
**below is my attempt to still work with it.
dA/dh = 1 times [-1(2pir^2h^-2) + 2pir
final answer: (-2pir^2h^-2) + 2pir
please can someone guide me on the technique i should use for getting the area to be in terms of h. any and all replies are welcome and appreciated

 

[Dick]

Don't ever double post again, ok?