I was finding it hard to understand why it wasn't differentiable (guess my maths is getting a bit rusty) until I read the below[0] which helped it make sense to

I was finding it hard to understand why it wasn't differentiable (guess my maths is getting a bit rusty) until I read the below[0] which helped it make sense to me: >The function has detail at every level, so zooming in on a piece of the curve does not show it getting progressively closer and closer to a straight line. Rather between any two points no matter how close, the function will not be monotone. [0] http://en.wikipedia.org/wiki/Weierstrass_function http://en.wikipedia.org/wiki/Weierstrass_function