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Khosrotash
  • Member for 10 years, 6 months
  • Last seen this week
40 votes
12 answers
28k views

Find the height of a bar, given the lengths of shadows cast by it and another bar

27 votes
15 answers
3k views

New Idea to prove $1+2x+3x^2+\cdots=(1-x)^{-2}$

20 votes
6 answers
1k views

Is there a geometric method to show $\sin x \sim x- \frac{x^3}{6}$

18 votes
13 answers
2k views

Wanted : for more formulas to find the area of a triangle?

17 votes
5 answers
2k views

When I was teaching absolute function properties, I suddenly made this question ...

17 votes
5 answers
2k views

Is there a way to solve for the missing angle?

10 votes
2 answers
622 views

Sum of angles under which a fixed line segment is seen from points situated on another line segment

10 votes
3 answers
298 views

Proving that: $\forall n \in \mathbb{N} :|f^{(n)}(x)|\leq \frac{1}{n+1}$

9 votes
5 answers
366 views

Ask about beautiful properties of $e$

9 votes
5 answers
478 views

$\sin 9^{\circ}$ or $\tan 8^{\circ} $ which one is bigger?

9 votes
3 answers
141 views

A summation question ,Is $S \to \ln 2$?

9 votes
3 answers
331 views

Is a visual proof to $\varphi = 1 + \tfrac{1}{{1 + \tfrac{1}{{1 + \tfrac{1}{{1 + \,\ddots\,}}}}}}$?

9 votes
4 answers
970 views

$\left\lfloor \frac{1}{\sqrt{1}}+\frac{1}{\sqrt{2}}+\frac{1}{\sqrt{3}}+\frac{1}{\sqrt{4}}+...+\frac{1}{\sqrt{1024}}\right\rfloor =?$

8 votes
6 answers
638 views

which one is bigger $100^n+99^n$ or $101^n$

7 votes
1 answer
155 views

Remainder of $35! $ when divided by $41$

7 votes
7 answers
274 views

Solve $\lfloor \sqrt x +\sqrt{x+1}+\sqrt{x+2}\rfloor=x$

7 votes
3 answers
193 views

$\frac{1}{1^2}+\frac{1}{1^2+2^2}+\frac{1}{1^2+2^2+3^2}+...\to ?\;\;$ (Click here.)

7 votes
1 answer
570 views

How prove $\cos 20^{\circ}$ is not rational?

7 votes
1 answer
422 views

How to prove $\sqrt 2 x + \sqrt {2{x^2} + 2x + 1} + \sqrt {2{x^2} - 10x + 13} + \sqrt {2{x^2} - 22x + 73} \geq \sqrt{157}$?

7 votes
6 answers
681 views

Other Idea to show an inequality $\dfrac{1}{\sqrt 1}+\dfrac{1}{\sqrt 2}+\dfrac{1}{\sqrt 3}+\cdots+\dfrac{1}{\sqrt n}\geq \sqrt n$

7 votes
5 answers
502 views

New idea to solve this equation

7 votes
6 answers
221 views

A new approach to find value of $x^2+\frac{1}{x^2}$

7 votes
5 answers
274 views

Finding non-zero function such that $f(2x)=f'(x)\cdot f''(x)$

7 votes
3 answers
236 views

Looking for an other method to compare $100!$ and $50^{100}$

7 votes
2 answers
531 views

How to fold a4 paper for 30 degree angle?

6 votes
2 answers
8k views

How many reflex angles can a polygon have? [closed]

5 votes
1 answer
273 views

Visualize Itô differentiation rule

5 votes
3 answers
154 views

Direct telescopic proof for sum of $1^2+2^2+...+n^2$

5 votes
2 answers
190 views

Nested radicals like Ramanujan's infinite radicals

5 votes
2 answers
2k views

Difference between Ito calculus and Malliavin calculus

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