Calculate the Iterated Integral $\int _ { 0 } ^ { \pi / 2 } \int _ { 0 } ^ { \pi / 2 } \sin ( x + y ) d y d x$

Short Answer

Calculate the iterated integral $\int _ { 0 } ^ { \pi / 2 } \int _ { 0 } ^ { \pi / 2 } \sin ( x + y ) d y d x$ .