1. The problem statement, all variables and given/known data Differentiate 2. Relevant equations 3. The attempt at a solution du/dx = cos(x) dv/du=cos(u) dg/dv=cos(v) dg/dx = dg/dv.dv/du.du/dx = cosx.cos(sinx).cos(sin(sinx)) I know the answer is correct but my issue is in the understanding of the solution given. I understand it all except the u = sin(x). The approach I take is to work from the inside to the outside by finding u as the inner most and g(v) as the outermost. What I don't understand is why isn't u = x? isnt that the inner most? Thanks.