Describe the Region Whose Area Is Given by the Integral $\int _ { 0 } ^ { \pi / 4 } \int _ { 0 } ^ { \cos 2 \theta } 2 r d r d \theta$

Describe the region whose area is given by the integral. $\int _ { 0 } ^ { \pi / 4 } \int _ { 0 } ^ { \cos 2 \theta } 2 r d r d \theta$