1. The problem statement, all variables and given/known data Hi I am trying to solve an indefinite integral of the form 1/ sqrt[ (x^2 +1)] dx.. 2. Relevant equations 3. The attempt at a solution Different ways of solving it are posted on the link below. I would like to know the following result : dx/y = dy/x = d (x+y)/ (x+y) ??? http://math.stackexchange.com/questions/610733/how-to-integrate-int-dx-over-sqrt1-x2?lq=1 Thanks.