1. The problem statement, all variables and given/known data Find the derivative of the function. Simplify where possible. arctan(x - sqrt(1+x2)) 2. Relevant equations Chain rule 3. The attempt at a solution let u = x - sqrt(1+x2) y = tan-1(u) dy/du = 1/(1+ u2) sub in u. dy/du = 1/1 + (x - sqrt(1+x2))2 du/dx = 1 - 1/2 (1+x2)-1/2 (2x) dy/dx = (1/1 + (x - sqrt(1+x2))2) (1 - 1/2 (1+x2)-1/2 (2x)) I always seem to forget 1 term and I am basically wondering if my method here is correct.