1. The problem statement, all variables and given/known data integrating a circle ,, my main question is that, can we integrate it by contour integration technique ? and if yes ,, would you plz show me how :) or just give me a hint :D Thanks is advance :-) 2. Relevant equations y^2 + x^2 = a^2 where a= r suppose that a = 2 3. The attempt at a solution i know that it can be done as two semicircles taking a substitution x=2sin(u) ,, or even by integration by parts!!!