Proving that a function is not totally differentiable in $(0,0)$
94193
determine whether $f(x, y) = \frac{xy^3}{x^2 + y^4}$ is differentiable at $(0, 0)$.
149764
If $f$ s twice differentiable and satisfies the following constraints, prove $f'(0)>-\sqrt 2$
16375
Is the function differentiable at $0$?
120784
Differentiablility over closed intervals
105068
Proving that the function is differentiable and $f'(0)=0$
150699
Show that if $f'$ is strictly increasing, then $\frac{f(x)}{x}$ is increasing over $(0,\infty)$
68774
Proving that $f(x)$ is less than or equal to $1+\pi/4$
15727
show that if $f$ is uniformly differentiable then prove that $f'$ is continuous
82567
Prove that $ f(x) $ has at least two real roots in $ (0,\pi) $
85092
Proving $ f(x) = x^2 $ is not uniformly continuous on the real line
117338
Counterexample to second derivative test when f''(x) is not continuously differentiable
142490
Alternative proof for differentiability of inverse function?
158681
How to show that $e^x$ is differentiable?
20273
Prove that if $|f(x)| \leq x^2$, then the function is continuous and differentiable at $x=0$.
28315
Monotone functions and non-vanishing of derivative
129324
Let $f:[0;1]\to\mathbb R$ be continiously differentiable
39057
Check the differentiablity of $\theta :\mathbb R^2 \setminus\{(0,0)\}\to \mathbb R$