求函数u=xsin(x+y)的在点(π/4,π/4)全微分

问题描述:

求函数u=xsin(x+y)的在点(π/4,π/4)全微分

du/dx=sin(x+y)+xcos(x+y)
du/dx=1
du/dy=xcos(x+y)=π/4cos(π/2)=0
du=dx+0dy=dx