y=sin(u-v)-cos(u+v) 求dy 用u,v,du,dv表示
问题描述：
y=sin(u-v)-cos(u+v) 求dy 用u,v,du,dv表示
答
∂y/∂u=cos(u-v)+sin(u+v)
∂y/∂v=-cos(u-v)+sin(u+v)
所以dy=[cos(u-v)+sin(u+v)]du+[-cos(u-v)+sin(u+v)]dv