1. The problem statement, all variables and given/known data Using the integral ∫dx/1+x^2 = pi/2 from 0 to infinity as a guide, introduce a parameter and then differentiate with respect to this parameter to evaluate the integral ∫dx/(x^2+a^2)^3 from 0 to infinity 2. Relevant equations 3. The attempt at a solution ∫(1/1+x^2) = tan^-1(x) introducing parameter x/a to replace x we get ∫(1/a)/(1+(x/a)^2) = tan^-1(x/a) ∫dx/(a^2+x^2) = 1/a*tan^-1(x/a) d/da(1/(x^2+a^2)) = -2a/(x^2+a^2)^2 im kind of stuck here. i don't really understand how to do this question, if anyone can help me understand/ lead me to the correct path that would be appreciated.