1. The problem statement, all variables and given/known data Find the following integral ∫1/(x*sqrt(x^2-1) dx 2. Relevant equations 3. The attempt at a solution I've decided to use the substitution: x = sec u dx = sec u * tan u du Substituting on the integral I got: ∫sec(u)*tan(u) / [sec u * sqrt((sec^2(u)-1))] du Since 1+tan^2(u) = sec^2(u) the integral simplifies to ∫ sec(u)*tan(u) / [sec(u)*tan(u)] du = ∫ du = u + c = sec(u) + c, c being an arbitrary constant. The answer on the solutions is given by the substitution u = sqrt(x^2-1) Is my answer wrong? Because it seems way simplier this way, and I don't see nothing wrong with the substitution... If anyone could help me I'd appreciate! Thanks.