所谓隐函数,是指不能化简成形如y=f(×)形式的函数。对于本题,同时对方程两边对x求导,由于y是×的函数,所以y对x求导则为y',详细步骤如下图:
arctany/x=㏑√(x²+y²)=½ln(x²+y²) 两边对x求导:
(y/x)'/[1+(y/x)²]=½(x²+y²)'/(x²+y²)
[(y'·x-y)/x²]/[1+(y/x)²]=½(2x+2y·y')/(x²+y²)
(y是x的函数,求导时要用到复合函数求导法则)
(y'·x-y)/(x²+y²)=(x+y·y')/(x²+y²)
y'·x-y=x+y·y'→y'(x-y)=x+y
y'=(x+y)/(x-y)
x^2-y^2 -4xy=0
2x -2y.dy/dx -4( x.dy/dx + y) =0
x -y.dy/dx -2( x.dy/dx + y) =0
(2x+y).dy/dx = x-2y
dy/dx = (x-2y)/(2x+y)