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robjohn

West Hills, CA

Age: 54

the mean square The Mean Square
(with one standard deviation and several unusual ones)

aka Rob Johnson

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Where would math be if Fermat had Post-it notes?

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Top Questions
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49
How to prove that $\lim\limits_{x\to0}\frac{\sin x}x=1$?
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33
How to prove a trigonometric identity
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29
Computing $\zeta(6)=\sum\limits_{k=1}^\infty \frac1{k^6}$ with Fourier series.
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29
Find a $4\times 4$ matrix $A$ where $A\neq I$ and $A^2 \neq I$, but $A^3 = I$.
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27
Question about a rotating cube?
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23
Compute: $\sum_{n=1}^{\infty}\dfrac {1\cdot 3\cdots (2n-1)} {2\cdot 4\cdots (2n)\cdot (2n+1)}$
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22
Proving the identity $\sum\limits_{k=1}^n {k^3} = \left(\sum\limits_{k=1}^n k\right)^2$ without induction
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22
AM-GM-HM Triplets
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21
Calculating $ \int _{0} ^{\infty} \frac{x^{3}}{e^{x}-1}\;dx$
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20
Evaluating $\int\limits_0^\infty \! \frac{x^{1/n}}{1+x^2} \ \mathrm{d}x$
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19
Why can the complex conjugate of a variable be treated as a constant when differentiating with respect to that variable?
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19
Is the integral $\int_0^\infty \frac{\mathrm{d} x}{(1+x^2)(1+x^a)}$ equal for all $a \neq 0$?
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19
How to evaluate $I=\displaystyle\int_0^{\pi/2}x^2\ln(\sin x)\ln(\cos x)dx$
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18
How to prove those “curious identities”?
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17
prove for all $n\geq 0$ that $3 | n^3+6n^2+11n+6$
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17
Question about Riemann integral and total variation
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16
Wrong Wolfram|Alpha limit?
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15
Does uncountable summation, with a finite sum, ever occur in mathematics?
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15
How to sum this series for $\pi/2$ directly?
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15
Does $|n^2 \cos n|$ diverge to $+\infty$?
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15
How to show that $\frac{\pi}{5}\leq\int_0^1 x^x\,dx\leq\frac{\pi}{4}$
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15
What is $-i$ exactly?
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14
A proof of $\int_{0}^{1}\left( \frac{\ln t}{1-t}\right)^2\,\mathrm{d}t=\frac{\pi^2}{3}$
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14
Nice expression for minimum of three variables?
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14
How to solve $\binom{n}{1}^2+2\binom{n}{2}^2 + 3\binom{n}{3}^2 + 4\binom{n}{4}^2+\cdots + n\binom{n}{n}^2$?
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14
How to get $ \cot(\theta/2)$ from $ \frac {\sin \theta} {1 - \cos \theta} $?
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14
Limit of $y=\sqrt{5+\sqrt{5-\sqrt{5+\sqrt{5-\sqrt{5+\ldots}}}}}$
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14
Finding the value of $\sum\limits_{k=0}^{\infty}\frac{2^{k}}{2^{2^{k}}+1}$
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13
Which integers are the areas of squares with vertices in the 3d integer lattice?
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13
If $f$ is measurable and $fg$ is in $L^1$ for all $g \in L^q$, must $f \in L^p$?
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