第4个回答 2021-01-04
画出积分区域D,是个以(0,0),(0,1),(1,1),(1,0)为顶点的正方形,画出直线y=x,将区域D分割成两部分,上面y>x,下面y<x
原式=∫[0,1]dy∫[0,y](y-x)dx +∫[0,1]dx∫[0,x](x-y)dy
=∫[0,1]【(yx-½x²)|[0,y]】dy +∫[0,1]【(xy-½y²)|[0,x]】dx
=∫[0,1](y²-½y²)dy +∫[0,1](x²-½x²)dx
=1/6 y^3|[0,1] +1/6 x^3|[0,1]
=1/6 +1/6
=1/3