已知dy/dx=2/2-cosy,求二阶导数d^2y/dx^2
问题描述：
已知dy/dx=2/2-cosy,求二阶导数d^2y/dx^2
答
直接对x求导就行啊，右边就是-(2/(2-cosy)^2)*(siny)*(2/(2-cosy))
答
dy/dx=2/(2-cosy)
即：
y'=2/(2-cosy)
y''
=-(2-cosy)'/(2-cosy)^2
=(cosy)'/(2-cosy)^2
=-siny*y'/(2-cosy)^2,将y'代入得到：
d^2y/dx^2 =y''=-2siny/(2-cosy)^3.