robjohn
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193,893
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 21h answered Calculate point coordinates from other points 1d answered arithmetic mean of smallest numbers of all subsets of r elements formed out of (1,2,..n) 2d revised Poisson distribution- mosquitos question fix typo 2d answered Poisson distribution- mosquitos question 2d comment Is there an inequality for $\sinh(x)$ which is similar to this inequality $\cosh(x)\leq e^{x^2/2}$ Doh! Sorry about that. 2d revised Contour Integral of $\int\limits_0^{2\pi}\frac{d\theta}{1+a\cos\theta}$ for $a^2<1$ (textbook wrong?) add a real method verification 2d comment Is there an inequality for $\sinh(x)$ which is similar to this inequality $\cosh(x)\leq e^{x^2/2}$ 2d revised Is there an inequality for $\sinh(x)$ which is similar to this inequality $\cosh(x)\leq e^{x^2/2}$ fix typo 2d answered Is there an inequality for $\sinh(x)$ which is similar to this inequality $\cosh(x)\leq e^{x^2/2}$ 2d answered Contour Integral of $\int\limits_0^{2\pi}\frac{d\theta}{1+a\cos\theta}$ for $a^2<1$ (textbook wrong?) Apr 25 comment Normal system of the least square method I thought you were wondering why the factor of $2$ was not in the derivative of $\|Pa-y\|$. I didn't think you were concerned about the factor of $2$ in $2P^T(Pa-y)=0$ since $2x=0\iff x=0$. What is it that is bothering you about the factor of $2$? Apr 25 comment Normal system of the least square method @MarcZ: If the addendum does not answer your question, let me know. Apr 25 revised Normal system of the least square method add some about the derivative of the norm Apr 25 revised Normal system of the least square method not necessarily a square matrix Apr 25 answered Normal system of the least square method Apr 24 revised How do I show that $\sum_{i = 1}^n \frac 1{\sqrt{a_n}} \lt \frac {\sqrt 3}6$ for $a_n = 4n(4n + 1)(4n + 2)$? add motivation Apr 24 comment How do I show that $\sum_{i = 1}^n \frac 1{\sqrt{a_n}} \lt \frac {\sqrt 3}6$ for $a_n = 4n(4n + 1)(4n + 2)$? I just realized that this is the same as Jack's answer, so I have added my motivation. Apr 24 answered How do I show that $\sum_{i = 1}^n \frac 1{\sqrt{a_n}} \lt \frac {\sqrt 3}6$ for $a_n = 4n(4n + 1)(4n + 2)$? Apr 24 comment Derivative of $\arctan y$ Please don't delete your question as soon as someone answers. This is not fair to the person who has answered your question. Apr 24 awarded Necromancer