Double integrals in polar

Let $R$‍ be the region inside the polar curves $r=\cos (\theta )$‍ and $r=-\sin (\theta )$‍, where $-{\displaystyle \frac{\pi }{2}}<\theta <-{\displaystyle \frac{\pi }{4}}$‍.

Let $f(x,y)=x^2+y^2$‍.