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 [tex]\int[/tex]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.