三角函数求导f(x,y)=sin(x-2y)fxy=?fyx=?

Question

三角函数求导
f(x,y)=sin(x-2y)
fxy=?
fyx=?

Answer 1

对f关于x求偏导,把y看成常数,fx=(sin(x-2y))'*(x-2y)'=cos(x-2y)*1=cos(x-2y)
对fx关于y求偏导,把x看成常数,fxy=(cos(x-2y))'(x-2y)'=-sin(x-2y)*(-2)=2sin(x-2y)
fy=-2cos(x-2y),fyx=2sin(x-2y)