Let $f:\mathbb{R}^2\to \mathbb{R}$ be any function. Then we know the following:
- Differentiability implies existence of partial derivatives and continuity
- Existence of partial derivatives does not imply continuity and hence not differnetiability.
- Continuity does not imply differentiability.
But now my question is "Does continuity of $f$ implies existence of partial derivatives?"
Best Answer
No. Take $f(x,y)=|x|$. It is continuous, but $\frac{\partial f}{\partial x}(0,0)$ doesn't exist.