https://math.codidact.com/categories/41/feed New Posts - Q&A - Mathematics Mathematics - Codidact 2020-10-25T02:56:32Z https://math.codidact.com/questions/278141 The probability distribution of rolling $n$ dice and keeping $k$ highest tommi https://math.codidact.com/users/53407 2020-09-19T17:57:38Z 2020-10-25T02:56:32Z <p>In many roleplaying games one rolls a handful of dice and calculates their sum. In some games there are bonus or penalty dice, so that we roll, for example, 4 dice with six sides and take the su... https://math.codidact.com/questions/278629 Why does the decimal expansion of $1/(10n - 1)$ have this neat pattern? Abheri Ragam https://math.codidact.com/users/53516 2020-10-19T19:07:53Z 2020-10-24T01:27:32Z <p>I was playing around with the reciprocals of some positive integers and found these interesting patterns:</p> <p>$$\frac{1}{19} = 0.\overline{052631578947368421}$$</p> <p>Now, this repeating d... https://math.codidact.com/questions/278696 Equation of a line given some parametrized points on it and an area msh210 https://math.codidact.com/users/8106 2020-10-21T13:56:43Z 2020-10-21T13:56:49Z <p>My kid has this question for homework:</p> <blockquote> <p>A line passing through the point $(6,6)$ crosses the line $y=2x$ at the point $A$, and the $x$-axis at the point $B$ (the $x$-coordinat... https://math.codidact.com/questions/278647 Method to calculate the area of a cyclic n-gon Razetime https://math.codidact.com/users/53310 2020-10-20T08:40:27Z 2020-10-20T09:15:01Z <p>The area of a cyclic quadriateral, given the side lengths, is given as follows: $$\sqrt{(s-a)(s-b)(s-c)(s-d)}$$</p> <p>(Brahmagupta's formula)</p> <p>Where $s = \frac{a+b+c+d}{2}.$</p> <p>I ... https://math.codidact.com/questions/278545 Using maximum of forecasted values to forecast maximum Guilherme Costa https://math.codidact.com/users/53453 2020-10-16T08:57:55Z 2020-10-18T07:06:15Z <p>I am using an algortihm to generate a daily sales forecast and have concluded that the forecast is, for pratical purposes, of good enough quality (&quot;low&quot; wMAPE).</p> <p>In general, and ... https://math.codidact.com/questions/278558 When and how should the $Z_n^2$ statistic be used? HDE 226868 https://math.codidact.com/users/36372 2020-10-16T20:10:54Z 2020-10-17T16:36:57Z <p>I was reading a paper (<a href="https://arxiv.org/abs/2010.06638">Kuechel et al. 2020</a>) claiming a detection of a high-frequency periodic signal coming from a known pulsar.<sup class="footnot... https://math.codidact.com/questions/278553 Which of the multiple definitions of correlation to use? Mithrandir24601 https://math.codidact.com/users/8162 2020-10-16T16:21:29Z 2020-10-17T15:32:48Z <p>In optics<sup class="footnote-ref"><a href="#fn1" id="fnref1">1</a></sup>, we have a notion of <a href="https://en.wikipedia.org/wiki/Degree_of_coherence#Degree_of_first-order_coherence">coheren... https://math.codidact.com/questions/278464 Discrete data: Graphs and skewness Nezar https://math.codidact.com/users/53471 2020-10-11T13:49:32Z 2020-10-15T10:49:47Z <p>I am studying an introductory course in statistic &quot; Essentials of Statistics&quot;. The author mentioned that Histograms are used to represent the frequency distribution of a contiuous data... https://math.codidact.com/questions/278430 Existence of a set of all sets MathPhysics https://math.codidact.com/users/53205 2020-10-09T08:44:55Z 2020-10-10T16:55:08Z <p>Suppose that we have an axiomatic set theory having the following axiom:</p> <p><strong>The Axiom Schema of Comprehension:</strong> Let $\mathbf{P}(x)$ be a property of $x$. For any set $A$, the... https://math.codidact.com/questions/278419 Can we adapt Furstenberg's proof of the infinitude of primes to other interesting subsets of the integers? HDE 226868 https://math.codidact.com/users/36372 2020-10-08T13:41:07Z 2020-10-09T01:22:39Z <p>In a textbook, I was introduced to <a href="https://en.wikipedia.org/wiki/Furstenberg%27s_proof_of_the_infinitude_of_primes">Furstenberg's topological proof of the infinitude of primes</a>, whic... https://math.codidact.com/questions/278332 Cutting the square Grove https://math.codidact.com/users/53452 2020-10-01T21:53:10Z 2020-10-07T15:22:09Z <p>I don't know how simple/diffcult this is, but it has been on my mind for some time, and I haven't managed to do anything about it, so now I'll try here to see if anyone has any input.</p> <p>Let... https://math.codidact.com/questions/278337 Similar triangles with the same area msh210 https://math.codidact.com/users/8106 2020-10-02T09:50:57Z 2020-10-05T02:25:00Z <p>My kid was assigned this problem:</p> <blockquote> <p>Given</p> <p><img src="https://math.codidact.com/uploads/N4FMPUuM5TMaqhhKXksq66mg" alt="line segments ADB, AEC, COE, and BOE;" /></p> <p>$\o... https://math.codidact.com/questions/278331 Including Association Analysis results into existing Classification Model Guilherme Costa https://math.codidact.com/users/53453 2020-10-01T21:13:15Z 2020-10-01T21:13:15Z <p>I have trained a <strong>classification model</strong> that predicts (returns a score) on how likely a customer is to buy from our company. This model <strong>does not contain any product specif... https://math.codidact.com/questions/278268 Asymptotics of counting integers by prime signature Peter Taylor https://math.codidact.com/users/36356 2020-09-28T14:30:12Z 2020-09-29T07:34:22Z <p>The prime counting function$\pi(n)$which counts the number of primes up to$n$is well-known, and it's also fairly well-known that using a well-optimised implementation of the <a href="https:/... https://math.codidact.com/questions/278280 Can we constructively find a third element of a set$X$satisfying$X \cong X \times X$given two distinct elements? Derek Elkins https://math.codidact.com/users/53398 2020-09-29T01:50:02Z 2020-09-29T01:50:02Z <p>Consider a set$X$such that$X \cong X\times X$. It's quite easy to prove in a classical set theory, e.g. <strong>ZF</strong>, that$X\$ must be the empty set or a singleton set or an infinite s... https://math.codidact.com/questions/278140 Computational hardness of the uniform halting problem user53100 https://math.codidact.com/users/53100 2020-09-18T17:12:41Z 2020-09-20T22:17:46Z <p>How hard is the decision-problem of a plain Turing Machine halting on all inputs? I'm not sure of the terminology, but by &quot;hard&quot; I mean its location on the arithmetical hierarchy.</p> ...