A question on differentiability at a point
1371
Prove that $f'(a)=\lim_{x\rightarrow a}f'(x)$.
94193
determine whether $f(x, y) = \frac{xy^3}{x^2 + y^4}$ is differentiable at $(0, 0)$.
25482
If a function is continuous and differentiable everywhere is the derivative continuous?
96973
If $F(0,0)=0$ and $F(x,y)= \frac{xy}{x^2+y^2}$ for $(x,y)\neq (0,0)$ then $F$ is differentiable at $(0,0)$?
148737
Is $|xy|$ differentiable in $(0,0)$?
69378
The derivative of $x!$ and its continuity
77624
Characterization of sets of differentiability
61481
Continuously Differentiable Curves in $\mathbb{R}^{d}$ and their Lebesgue Measure
49587
Does a differentiable everywhere function have a continuous derivative?
37850
Does the everywhere differentiability of $f$ imply it is absolutely continuous on a compact interval?
61486
Show that $f$ is not differentiable at $(0,0)$ - $\frac{x_1^2x_2}{x_1^2+x_2^2}$
93528
Continuous versus differentiable
117338
Counterexample to second derivative test when f''(x) is not continuously differentiable
66560
Is a differentiable function always continuous?
158681
How to show that $e^x$ is differentiable?
46923
Differentiable Sequences
128975
Behavior of $\|f\|_p$ when $p$ is near the endpoint of $I$