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wlad's user avatar
wlad
  • Member for 9 years
  • Last seen more than a week ago
27 votes

How to prove that $\lim\limits_{x\to0}\frac{\sin x}x=1$?

20 votes

Unexpected examples of natural logarithm

17 votes
Accepted

When is $32x+32$ a square number?

16 votes

Are all continuous one one functions differentiable?

15 votes
Accepted

A freshman's dream

10 votes

Different ways finding the derivative of $\sin$ and $\cos$.

9 votes
Accepted

The order of group $G$ is odd. Prove the mapping $f:G\to G$ by $f(x) = x^2$ is injective.

9 votes

Are there mathematical objects that have been proved to exist but cannot be described in words?

9 votes

Show that if $\mathcal{P}(A) \subseteq A $ then $ \mathcal{P}(A) \in A $.

8 votes

How can you find a Pythagorean triple with $a^2+b^2=c^2$ and $a/b$ close to $5/7$?

7 votes

How can I show that $\sqrt{1+\sqrt{2+\sqrt{3+\sqrt\ldots}}}$ exists?

7 votes
Accepted

The value of the sum $\binom {20}0 -\binom {20}2+ \binom{20}4-...-\binom{20}{18}+\binom{20}{20}$

7 votes
Accepted

Preimage of $f:(x,y,z)\mapsto x^2+y^2+z^2+2x+5$

7 votes

Different ways finding the derivative of $\sin$ and $\cos$.

7 votes

How to prove that the Fibonacci sequence is periodic mod 5 without using induction?

6 votes

How to solve $4^x+\sin(x)=10$

6 votes
Accepted

Prove a norm inequality by Lagrange multipliers

6 votes

Give an example of: A group with an element A of order 3, an element B with order 4, where order of AB is less than 12

5 votes

How can I show that $\sqrt{1+\sqrt{2+\sqrt{3+\sqrt\ldots}}}$ exists?

5 votes

What is the dicyclic group of order $12$? (What is $\mathbb{Z}_3\rtimes \mathbb{Z}_4$)

5 votes

Let $f: [-1, 1] \longrightarrow [-1, 1]$ such that $f\in C^{1}$. Prove that there's exist $x_{0} \in [-1, 1]$ such that $|f'(x_{0})| \leq 1$

5 votes

What is the area bounded by the graph of $ \lfloor x \rfloor + \lfloor y \rfloor =2 $ with the $x$ and $y$-axis?

5 votes

Monotonicity of $\frac{n}{\sqrt[n]{(n!)}}$

5 votes

An example of a group such that $G \cong G \times G$

5 votes

How many ways can a woman polish her nails if she uses one of two colors on each nail?

5 votes
Accepted

Proving that the delta function is the derivative of the step function.

5 votes

Give an intuitive explanation for polynomial quotient ring, or polynomial ring mod kernel

4 votes

sumation question

4 votes

Integer solutions to $x^{x-2}=y^{x-1}$

4 votes

Enumerations of the rationals with summable gaps $(q_i-q_{i-1})^2$

1
2 3 4 5
7