query: Find a function $f :\Bbb R^2\to \Bbb R$ which is not differentiable at $(0,0)$ even though all directional derivatives of $f$ exist at $(0,0).$
positive_passages.docid: 144426
positive_passages.text: Example of a function $f:\mathbb{R}^2\to\mathbb{R}$ not differentiable at $(0,0)$, but has a directional derivative at $(0,0)$ in all directions
negative_passages.docid: 39057
negative_passages.text: Check the differentiablity of $\theta :\mathbb R^2 \setminus\{(0,0)\}\to \mathbb R$
negative_passages.docid: 2506
negative_passages.text: twice differentiable functions
negative_passages.docid: 12726
negative_passages.text: Differentiating both sides of a non-differential equation
negative_passages.docid: 88463
negative_passages.text: What is an example of Gâteaux differentiable but not Fréchet differentiable at a point in a finite-dimensional space?
negative_passages.docid: 69845
negative_passages.text: Construct a real function with is exactly $C^2$ such that its first derivative does not vanish everywhere
negative_passages.docid: 143593
negative_passages.text: A sequence of differentiable functions that converge uniformly to a non differentiable function - is my example correct?
negative_passages.docid: 7861
negative_passages.text: Non-analytic smooth function
negative_passages.docid: 5625
negative_passages.text: Entire function with vanishing derivatives?
negative_passages.docid: 150833
negative_passages.text: Discontinuities of the derivative of a differentiable function on closed interval
negative_passages.docid: 35264
negative_passages.text: Must a monotone function have a monotone derivative?
negative_passages.docid: 54137
negative_passages.text: Find a non-negative function on [0,1] such that $t\cdot m(\{x:f(x) \geq t\}) \to 0$ that is not Lebesgue Integrable
negative_passages.docid: 58816
negative_passages.text: Existence of a continuous function which does not achieve a maximum.
negative_passages.docid: 38192
negative_passages.text: Derivative of inverse function at a point.
negative_passages.docid: 37736
negative_passages.text: How to find a function in $ L_{2}(0,\infty)$ but not $L_{q}(0,\infty)$, $q\neq 2 $
negative_passages.docid: 135610
negative_passages.text: How to give an example of a $f$ differentiable in a deleted neighborhood of $x_0$ such that $\lim_{x\to x_0}f^\prime(x)$ doesn't exist?
negative_passages.docid: 93967
negative_passages.text: Prove partial derivatives exist, but not all directional derivatives exists.