1. The problem statement, all variables and given/known data Evaluate the derivative of the following function: f(w)= cos(sin^(-1)2w) 2. Relevant equations Chain Rule 3. The attempt at a solution I did just as the chain rule says where F'(w)= -[2sin(sin^(-1)2w)]/[sqrt(1-4w^(2)) but the book gave the answer as F'(w)=(-4w)/sqrt(1-4w^(2)) and I'm wondering if there is some kind of simplification I'm missing. Why would sin and sin^(-1) disappear?