Which function is not differentiable at x = 0?

f(x) = x²

f(x) = |x|

f(x) = sin(x)

f(x) = eˣ

f(x) = |x| has a cusp at x = 0, making it non-differentiable there.

A function is differentiable at a point if its derivative exists at that point.

The absolute value function, (f(x)=|x|), has a sharp corner at (x=0).

Functions with sharp corners are not differentiable at those points.