1. The problem statement, all variables and given/known data Find the 100th derivative at 1 of f(x) = x/(1+x^2) 2. Relevant equations 3. The attempt at a solution For |x| < 1 I can write f as a power series (since 1/(1+x^2) = sum_n (-1)^n x^(2n)) but this won't work at 1. I tried writing out the first few derivatives at 1 explicitly but things got pretty messy. Any ideas?