Chapter 13.3, Problem 26E

Cartesian to polar coordinates Sketch the given region of integration R and evaluate the integral over R using polar coordinates.

26.     ${\displaystyle \underset{R}{\iint }\frac{dA}{1+x^2+y^2};}$ R = {(r, θ): 1 ≤ r ≤ 2, 0 ≤ θ ≤ π}