# Math Help - Switch to polars to evaluate integral

1. ## Switch to polars to evaluate integral

For $b>0, a - b > 1$, let $f_{ab}(x,y) = |xy|^b / (x^2+y^2+1)^a$. Use polar coordinates to integrate $f_{ab}$ over $\Re^2$.

2. Originally Posted by Amanda1990
For $b>0, a - b > 1$, let $f_{ab}(x,y) = |xy|^b / (x^2+y^2+1)^a$. Use polar coordinates to integrate $f_{ab}$ over $\Re^2$.
Looks pretty straightforward to me. In polar coordinates $x= r cos(\theta)$ and $y= r sin(\theta)$ so $|xy|^b= r^{2b}|cos(\theta)sin(\theta)|^b$ and $x^2+ y^2+ 1= r^2+ 1$. What is dxdy?

3. Well yes, I can find all the terms, I just can't do the integral!