# Not possible to find a function g such that g

1. Jul 31, 2009

### squenshl

Why is it not possible to find a function g such that g $$\in$$ C1 at (0,0) and g is not differentiable at (0,0)

2. Jul 31, 2009

### squenshl

Re: Differentiability

Also given that f(x,y) = x|y| how do I show that f $$\notin$$ C1 at (0,0)

3. Jul 31, 2009

### slider142

Re: Differentiability

As far as I know, a function is defined to be C1 if it is continuously differentiable, so the question doesn't make sense.

4. Jul 31, 2009

### slider142

Re: Differentiability

Remember the definition of differentiability: all approaches to the point (0,0) must yield the same derivative. Consider approaching the derivative along the x-axis and then the derivative along the y-axis. Are they equal?