Use polar coordinates to set up and evaluate the double integral ∬_(R)f(x,y)dA.
(a) f(x,y)=x+y;R:x^(2)+y^(2)<=4,x>=0,y>=0.
(b) f(x,y)=arctan((y)/(x)),R:x^(2)+y^(2)>=1,x^(2)+y^(2)<=4,0<=y<=x.
2. Use polar coordinates to set up and evaluate the double integral ∬_(R)f(x,y)dA where f(x,y)=x+y;R:x^(2)+y^(2)<=4