|(f(x) - f(0)) / (x - 0)| = |f(x) / x| <= x^2, so f'(x) exists.
Determine whether or not the derivative for the function f(x) below exists at x=0. Find f'(x) if exists.
f(x) = { x^3 * cos (1/x) if x != 0
{ 0 if x = 0
I'm sorry for being stupid. I personally think this problem is not hard
And also I don't know how to do math code so forgive me
Thank you in advance.