计算∬Dx2ycos(xy2)dxdy,D:0≤x≤π/2,0≤y≤2
∬Dx2ycos(xy2)dxdy=∫0π/2dx∫02x2ycos(xy2)dy =∫0π/2(1/2)x[sin(xy2)]|02dx=1/2∫0π/2xsin4xdx =1/2[(1/16)sin4x-(1/4xcos4x)]|0π/2=-(π/16)
计算∬Dx2ycos(xy2)dxdy,D:0≤x≤π/2,0≤y≤2
∬Dx2ycos(xy2)dxdy=∫0π/2dx∫02x2ycos(xy2)dy =∫0π/2(1/2)x[sin(xy2)]|02dx=1/2∫0π/2xsin4xdx =1/2[(1/16)sin4x-(1/4xcos4x)]|0π/2=-(π/16)