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abel
  • Member for 12 years, 11 months
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36 votes
Accepted

Trace of AB = Trace of BA

30 votes

Does the square or the circle have the greater perimeter? A surprisingly hard problem for high schoolers

21 votes

Non-zero eigenvalues of $AA^T$ and $A^TA$

17 votes
Accepted

Show that $f(x) = \frac{x^3}{1+x^2}$ is bijective

16 votes

Determine a matrix knowing its eigenvalues and eigenvectors

16 votes

Why are eigenvalues of nilpotent matrices equal to zero?

15 votes

Limit of $\frac{1}{\sqrt[n]{n!}}$ as $n$ approaches infinity

13 votes
Accepted

Matrices such that $M^2+M^T=I_n$ are invertible

12 votes

Show that 1 and -1 are the only eigenvalues of this linear transformation

11 votes

how to prove plane $ax+by+cz = d$ has normal vector $(a,b,c)$

10 votes
Accepted

Exercise: Evaluating integration $\int_{|z|=r} \frac{1}{(z-a)(z-b)}dz$, $|a|<r<|b|$

10 votes

Is there a vector field that is equal to its own curl?

10 votes

All matrices which commute with all $2\times 2$ matrices

10 votes

Prove that equation $x^6+x^5-x^4-x^3+x^2+x-1=0$ has two real roots

10 votes
Accepted

$\sin x + c_1 = \cos x + c_2$

9 votes
Accepted

How many orthogonal matrices are there

9 votes

Which quantity is greater, $\frac{x^2}{y+\frac1y}$ or $\frac{y^2}{x+\frac1x}$?

9 votes
Accepted

Why do we need two linearly independent solutions for 2nd order linear ODE

8 votes
Accepted

Listing all the possible echelon forms of a $3\times 3$ matrix

8 votes
Accepted

Proving sine of sum identity for all angles

8 votes
Accepted

Number of real roots of the equation $(6-x)^4+(8-x)^4 = 16$

8 votes

Column Space and SVD

8 votes

SAT Maths Question About Fractions

8 votes
Accepted

To evaluate $\lim_{n\to\infty} \frac{10^n}{n!} .$

7 votes

Prove that $\sin 2\alpha=2 \sin \alpha \cos\alpha$

7 votes
Accepted

Differential equation: $\frac {dy}{dx}=\frac {1}{x \cos y +\sin 2y}$

7 votes
Accepted

Is $\text{rank} (A^*A)=\text{rank}(A)$ for all nonsquare matrices?

7 votes

Help me solve $\int \ln(2x+1)dx$

6 votes

Distance of two lines in $\mathbb{R}^3$

6 votes
Accepted

How to evaluate $\int \sin^{-1}(x)\cos^{-1}(x) \, dx$?

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