## [SOLVED] derivative question

I feel like Im missing something here...
I know the definition for a derivative and all that, but I cant seem to be able to prove this simple question:
show that f(x) is differentiable at x=0:
f(x)={x^2 if x is rational and 0 if x is irrational}
all the examples I can find are not for piecewise functions like this.