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27
Is a function periodic $f(x) = \cos (x) +\cos(x^2)$
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13
Example of a function differentiable in a point, but not continuous in a neighborhood of the point?
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11
$A^{64}=A^{27}=I$, prove $A=I$
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10
Is this a valid argument for proving that a sum of reciprocals is irrational?
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10
If $f'(x)>0$ on $E$ , where $m(E)>0,$ then $m(f(E))>0$
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9
Why is a polynomial $f(x)$ sum of squares if $f(x)>0 $ for all real values of $x$?
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8
Negative moments of Marchenko-Pastur law
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6
Is there any function continuous in $R$ and differentiable in rational numbers with zero derivative?
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6
Can $\sigma(p^k)=2^n$ for some $k>1$?
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6
The minimal combination $\big|\pm p_1\pm\dots\pm p_n\big|$ for primes
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6
How to evaluate $1 - \frac{\binom{n^2}{1}}{\binom{n+1}{1}} + \frac{\binom{n^2}{2}}{\binom{n+2}{2}} - \frac{\binom{n^2}{3}}{\binom{n+3}{3}} + ..$
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6
Examples of functions where $f'(x)=f(f(x))$ for all $x$
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5
Showing that if a function between metric spaces has Hölder exponent $\alpha > 1$, this function must be constant
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5
Does the Zygmund class on a closed interval include all everywhere differentiable functions?
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5
Provided that $A$ is a $n \times n$ real matrix, $A^2＝0$, is it true that $\operatorname{rank}(A+A^\text{T})＝2\times\operatorname{rank}(A)$?
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