Question

反函数的二阶导

Answer 1

dx/dy = 1/(dy/dx) = 1/ y'

d²x/dy² = d(dx/dy) /dy = [d(dx/dy) /dx] * (dx/dy ) 复合函数求导

= (1/y') ' * (1/y')

= - y'' /(y')² * (1/y') = - y'' / (y')³