1. The problem statement, all variables and given/known data The question I am trying to answer requires me to find the following: dN/dS ∝ S^−5/2/cosh(r/R) and I am giving the follwing equation in the question. A=4πR^2 sinh^2〖(r/R)〗 3. The attempt at a solution Right I know how to get the S^-5/2 in the top half of the equation. I also understand that the cosh part comes from the differentiation of A. The problem I have is after applying the product rule to A I end up with this: dA/dr=8πRsinh^2 (r/R)+ 8πR^2 sinh(r/R)cosh(r/R) I am stuck on how the terms cancel to leave me with cosh(r/R) so i can reach the equation required.