1. The problem statement, all variables and given/known data Find the integral from 0 to pi/2 of sin(x)dx/(cos(x)+sin(x)). 3. The attempt at a solution You can easily make it into the integral of tan(x)dx/(1+tan(x)), but the substitution u=tanx can't work because tan(pi/2) is undefined. Any ideas for a good substitution?