robjohn

West Hills, CA

http://none

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

aka Rob Johnson

$\LaTeX$ support for Chat

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How to sum this series for $\pi/2$ directly?

sequences-and-series pi asked Oct 31, 2011 at 19:17

math.stackexchange.com

39 votes

MathJax CDN (cdn.mathjax.org) will be shutting down

support mathjax asked Apr 1, 2017 at 17:59

meta.stackexchange.com

21 votes

Drawing Rotated views while ignoring the Bounding box

graphics asked Mar 3, 2012 at 19:13

mathematica.stackexchange.com

15 votes

Asymptotic Expansion for $\frac1{2^n}\sum_{k=1}^n\frac1{\sqrt{k}}\binom{n}{k}$

probability asymptotics binomial-distribution asked May 31, 2019 at 16:19

math.stackexchange.com

12 votes

Why is there a discrepancy between JoinedCurve/FilledCurve and the underlying BSplineCurve segments?

graphics splines asked Oct 31, 2020 at 20:44

mathematica.stackexchange.com

12 votes

Why does $\tan(30^{\large\circ})=\frac{\tan(10^{\large\circ})\tan(50^{\large\circ})}{\tan(20^{\large\circ})}$?

trigonometry asked Apr 29, 2020 at 6:14

math.stackexchange.com

9 votes

Rotational oblateness

newtonian-gravity rotational-dynamics planets centrifugal-force geophysics asked Jun 29, 2013 at 20:43

physics.stackexchange.com

9 votes

Is $\left(1+\frac1n\right)^{n+1/2}$ decreasing?

inequality exponential-function cauchy-schwarz-inequality eulers-number asked Jun 11, 2019 at 22:25

math.stackexchange.com

7 votes

Cannot Get Numerical Results to Match

numerical-integration special-functions accuracy precision asked Mar 16, 2013 at 0:23

mathematica.stackexchange.com

6 votes

Texture prevents JoinedCurve from closing

graphics bugs splines filling textures asked Feb 2, 2021 at 14:29

mathematica.stackexchange.com

Top Answers

638

How to prove that $\lim\limits_{x\to0}\frac{\sin x}x=1$?

math.stackexchange.com

177

What's 4 times more likely than 80%?

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151

Slice of pizza with no crust

math.stackexchange.com

143

How to prove that $\frac{\zeta(2) }{2}+\frac{\zeta (4)}{2^3}+\frac{\zeta (6)}{2^5}+\frac{\zeta (8)}{2^7}+\cdots=1$?

math.stackexchange.com

128

Parabola is an ellipse, but with one focal point at infinity

math.stackexchange.com

105

Is it possible to represent every irrational number as a (limit of) an infinite sum of rational numbers?

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Proving an alternating Euler sum: $\sum_{k=1}^{\infty} \frac{(-1)^{k+1} H_k}{k} = \frac{1}{2} \zeta(2) - \frac{1}{2} \log^2 2$

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Is there any integral for the Golden Ratio?

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Arc length contest! Minimize the arc length of $f(x)$ when given three conditions.

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Computing $\zeta(6)=\sum\limits_{k=1}^\infty \frac1{k^6}$ with Fourier series.

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Can an infinite sum of irrational numbers be rational?

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Is it possible to write a sum as an integral to solve it?

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Evaluating $\int_0^\infty \sin x^2\, dx$ with real methods?

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In which cases is the inverse of a matrix equal to its transpose?

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To sum $1+2+3+\cdots$ to $-\frac1{12}$

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Evaluating $\lim\limits_{n\to\infty} e^{-n} \sum\limits_{k=0}^{n} \frac{n^k}{k!}$

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Are all limits solvable without L'Hôpital Rule or Series Expansion

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I have a problem understanding the proof of Rencontres numbers (Derangements)

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Trivial zeros of the Riemann Zeta function

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Generalized Euler sum $\sum_{n=1}^\infty \frac{H_n}{n^q}$

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A closed form of $\int_0^\infty\frac{\sqrt[\phi]{x}\ \arctan x}{\left(x^\phi+1\right)^2}dx$

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How to evaluate $\int_0^{\pi/2}x^2\ln(\sin x)\ln(\cos x)\ \mathrm dx$

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Why is $i^3$ (the complex number "$i$") equal to $-i$ instead of $i$?

math.stackexchange.com

How to prove a trigonometric identity $\tan(A)=\frac{\sin2A}{1+\cos 2A}$

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Prove that $\lim \limits_{n \to \infty} \frac{x^n}{n!} = 0$, $x \in \Bbb R$.

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Linear diophantine equation $100x - 23y = -19$

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Question about a rotating cube?

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Coin flipping probability game ; 7 flips vs 8 flips

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Why can the complex conjugate of a variable be treated as a constant when differentiating with respect to that variable?

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Curious Integral Proof

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