1. The problem statement, all variables and given/known data
Find a function f : [-1,1] ---> R such that f satisfies the following properties:
a) f is continuous
b) f is restricted to (-1,1) is differentiable
c) its derivative f' is not differentiable on (-1,1)
2. Relevant equations
3. The attempt at a solution
I kinda think that the mean value theorem and Theorem 2 of the fundamentals f(x)dx = F(b)-F(a) got some link but I can't seem to get it. I do understand that for f'' not to exist, x should be undefined on the (-1,1). Please help.