u=x(z+y) z=sin(x+y) 求二阶偏导数σ2u/σxσy
问题描述:
u=x(z+y) z=sin(x+y) 求二阶偏导数σ2u/σxσy
答
σu/σx=(z+y)+x(σz/σx+0)=z+y+xcos(x+y)
σ2u/σxσy=σz/σy+1-xsin(x+y)=cos(x+y)+1-xsin(x+y)