# Double integral with polar

1. Nov 12, 2007

### Renzokuken

1. Integrate f(x,y)=x+y
1<=x^2+y^2<=4, x>=0, y>=0

3. ∬x+y dxdy x=rcos(o) y=rsin(o)

∬r(rcos(o)+rsin(o))drdo
r is from 1 to 4, o is from 0 to pi/2

I get the wrong answer and don't know why

2. Nov 12, 2007

### bob1182006

$$x^2+y^2=r^2$$

r doesn't go from 1 to 4. r^2 goes from 1 to 4.
the 0 to pi/2 seems good.

Don't know about the rest of the integral though sorry haven't learned polars yet :/