1. The problem statement, all variables and given/known data I have this question in my text and the answer has a sec^2 in it, and according to what I know, there is no where that you need to use derivatives, but maybe I dont understand the formula? Up until now all the answers have just been regular functions, not derivatives. ANyways, here is what i've done Question is C is a positively oriented boundary of the square whose sides lie on lines x & y = +/- 2 so eval Int_c tan(z/2) / (z-x_0)^2 dz The answer in the text is i*pi*sec^2(x_0)/2 2. Relevant equations The Cauchy Integral formula I'm using is as follows f(z_0) = 1/ (2 * pi * i) ⌠_c f(x) / (z-z_0) dz 3. The attempt at a solution modified the intergral so I could use the above formula ⌠_c tan(z/2) / (z-x_0)(z+x_0) dz so f(x) = tan(z/2) / (z+x_0) and z_0 = x_0 so f(z_0) = tan(x_0/2) / (2x_0) Using Cauchy Integral I get tan(x_0/2) / (2x_0) * (2 * pi * i) so the 2's cancel and I get p * i * tan(x_0 / 2) / x_0 What don't I know about sec^2 (x) that makes me not be able to get the answer?