Tricky intergral

1. Nov 12, 2006

Lee

Which substituation would I need to use for this intergral;

[y.du/(y^2 + (x - u)^2)]

2. Nov 12, 2006

Galileo

The integrand looks like $$1/(1+x^2)$$ which has antiderivative arctan(x). Try to make substitutions to match that expression.

3. Nov 13, 2006

Lee

Got it, take the y out the intergral, make b=x-u then db=-du sub in and use the arctan intergral, getting -tan^-1((x-u)/y)