题目设闭区域D由直线x=0,y=pi,y=x围成,则iint_(D)cos(x+y)dx dy=().A. -2B. -1C. 2D. 1设闭区域$D$由直线$x=0$,$y=\pi$,$y=x$围成,则$\iint_{D}\cos(x+y)dx dy=$().A. -2B. -1C. 2D. 1题目解答答案A. -2