Using polar coordinates evaluate

int int over D 3(x+y) and D is x^2 + y^2 <=9, x>=0

Ok, I have

int (between -pi/2 and pi/2) d theta . int(between 3 and 0) 3r^2(costheta + sintheta)

giving 18

is this right?

it seems i'm missing something I think

many thanks