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