# Double integral

1. Aug 4, 2009

### squenshl

For the double integral $$\int\int_R$$ sqrt(x^2+y^2) dx dy where R is the unit circle.
I got$$\int_0^\pi\int_1^1$$ sqrt(r2) r dr dtheta
Then after the integration I got an answer of 2$$pi$$/3 as my final answer.
Is this right.
The bottom of the 2nd integral is -1 not 1

2. Aug 4, 2009

### tiny-tim

Hi squenshl!

(have a pi: π and a theta: θ and try using the X2 tag just above the Reply box )

(and you needed \int_{-1}^1)

erm you can't have r less than 0!!