Evaluate $\iint _ { R } \frac { \sin ( x + y ) } { \cos ( x - y ) } d A$

Short Answer

Evaluate $\iint _ { R } \frac { \sin ( x + y ) } { \cos ( x - y ) } d A$ ,where R is the rectangular region bounded by the lines x + y = 0, $x + y = \frac { \pi } { 2 }$ , x - y = 0, and $x - y = \frac { \pi } { 4 }$ .