User marwalix

94 votes

I'm trying to find the longest consecutive set of composite numbers

answered Jun 6, 2017 at 6:52

65 votes

Accepted

Why is $1/i$ equal to $-i$?

answered May 11, 2015 at 12:15

35 votes

Accepted

Do the Liouville Numbers form a field?

answered Mar 29, 2015 at 14:10

15 votes

Does a symmetric matrix with all entries $0$ or $1$ and with diagonal $0$ have integer eigenvalues?

answered Feb 8, 2015 at 10:50

15 votes

Accepted

Why is $A = \begin{bmatrix} 0 & 1 \\ 0 & 0 \end{bmatrix}$ not diagonalizable

answered Oct 17, 2016 at 21:46

13 votes

What is wrong with this limit reasoning

answered Apr 29, 2015 at 11:44

13 votes

Accepted

Prove that the orthogonal projection operator is idempotent

answered Dec 14, 2015 at 5:59

12 votes

When a determinant is zero

answered Feb 8, 2015 at 11:54

12 votes

Proving that $\sqrt[3] 7 -\sqrt 2$ is irrational.

answered Apr 16, 2021 at 19:45

10 votes

Accepted

For any rng $R$, can we attach a unity?

answered May 27, 2015 at 18:44

10 votes

Accepted

How to prove $\sqrt3 + \sqrt[3]{2}$ is a irrational number?

answered May 14, 2016 at 16:12

10 votes

Accepted

Find all positive integers $x$ and $y$ for which $\frac{1}{x} + \frac{1}{y} = \frac{1}{p}.$

answered Jul 18, 2020 at 10:04

10 votes

Accepted

Complex Derivatives in Polar Form

answered Jan 15, 2018 at 10:49

10 votes

Find the determinant of $I + A$

answered Oct 16, 2016 at 11:36

10 votes

Are homeomorphisms convex-preserving?

answered Jan 16, 2017 at 6:59

9 votes

What is the value of this improper integral? $\lim_{x\rightarrow 0 } \dfrac{1}{x} \int_{x}^{2x} e^{-t^2}\,\mathrm dt$

answered Dec 14, 2015 at 5:37

9 votes

Accepted

What's wrong in this equation? (Regarding Euler's eqn)

answered Apr 17, 2015 at 20:16

9 votes

Accepted

Show that the set $\mathbb{Q}[\sqrt{2}] = \{a + b \sqrt{2} \mid a, b \in \mathbb{Q}\}$ is a field with the usual multiplication and addition.

answered Apr 26, 2018 at 15:47

8 votes

Accepted

How can I find the indefinite integral of $\int\sin^3x \cos^3x dx $?

answered May 6, 2015 at 16:00

8 votes

Accepted

Relationship between trigonometric and hyperbolic sine

answered Feb 1, 2015 at 9:25

8 votes

Does set $\mathbb{R}^+$ include zero?

answered Aug 6, 2010 at 16:11

8 votes

Accepted

A simple inequality looking for a more elegant proof...

answered Mar 2, 2015 at 16:04

8 votes

Accepted

Is there a definite integral that evaluates to the constant $e$?

answered Mar 8, 2015 at 20:34

8 votes

If $a,b \in \mathbb{C}$ are transcendental over $\mathbb{Q}$ then is $a^b$ necessarily transcendental over $\mathbb{Q}$?

answered Jun 12, 2016 at 10:36

7 votes

Why are the coefficients always equal?

answered Jun 30, 2015 at 9:57

7 votes

Accepted

Matrix exponential: $\begin{pmatrix} 0 & 1 \\ -4 & 0 \end{pmatrix}$

answered Sep 2, 2015 at 10:43

7 votes

Evaluate the limit $\lim_{x \to \frac{\pi}{4}} \frac{1-\tan x}{x-\frac{\pi}{4}}$

answered Feb 28, 2017 at 13:48

7 votes

Accepted

Show that $a^2 \not\equiv b^2 \pmod p$

answered Sep 3, 2019 at 5:26

7 votes

Prove that $\sum\limits_{i=1}^{k} \cos^2\left(\frac{2i\pi}{k}\right) = \frac{k}{2}$

answered Feb 14, 2018 at 21:30

7 votes

Accepted

If $B$ is invertible then there exists a scalar $c$ such that $A+cB$ is not invertible

answered Jun 13, 2017 at 7:08

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695 Answers

I'm trying to find the longest consecutive set of composite numbers

Why is $1/i$ equal to $-i$?

Do the Liouville Numbers form a field?

Does a symmetric matrix with all entries $0$ or $1$ and with diagonal $0$ have integer eigenvalues?

Why is $A = \begin{bmatrix} 0 & 1 \\ 0 & 0 \end{bmatrix}$ not diagonalizable

What is wrong with this limit reasoning

Prove that the orthogonal projection operator is idempotent

When a determinant is zero

Proving that $\sqrt[3] 7 -\sqrt 2$ is irrational.

For any rng $R$, can we attach a unity?

How to prove $\sqrt3 + \sqrt[3]{2}$ is a irrational number?

Find all positive integers $x$ and $y$ for which $\frac{1}{x} + \frac{1}{y} = \frac{1}{p}.$

Complex Derivatives in Polar Form

Find the determinant of $I + A$

Are homeomorphisms convex-preserving?

What is the value of this improper integral? $\lim_{x\rightarrow 0 } \dfrac{1}{x} \int_{x}^{2x} e^{-t^2}\,\mathrm dt$

What's wrong in this equation? (Regarding Euler's eqn)

Show that the set $\mathbb{Q}[\sqrt{2}] = \{a + b \sqrt{2} \mid a, b \in \mathbb{Q}\}$ is a field with the usual multiplication and addition.

How can I find the indefinite integral of $\int\sin^3x \cos^3x dx $?

Relationship between trigonometric and hyperbolic sine

Does set $\mathbb{R}^+$ include zero?

A simple inequality looking for a more elegant proof...

Is there a definite integral that evaluates to the constant $e$?

If $a,b \in \mathbb{C}$ are transcendental over $\mathbb{Q}$ then is $a^b$ necessarily transcendental over $\mathbb{Q}$?

Why are the coefficients always equal?

Matrix exponential: $\begin{pmatrix} 0 & 1 \\ -4 & 0 \end{pmatrix}$

Evaluate the limit $\lim_{x \to \frac{\pi}{4}} \frac{1-\tan x}{x-\frac{\pi}{4}}$

Show that $a^2 \not\equiv b^2 \pmod p$

Prove that $\sum\limits_{i=1}^{k} \cos^2\left(\frac{2i\pi}{k}\right) = \frac{k}{2}$

If $B$ is invertible then there exists a scalar $c$ such that $A+cB$ is not invertible