For questions related to usage of Wolfram Alpha.

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5
votes
1answer
148 views

Why does WolframAlpha give a strange solution set to $\lfloor a\rfloor=0$?

I decided to go and look up the roots of $\lfloor a\rfloor$ in WolframAlpha where $a$ is any number, real or complex, and of course the interval $[0,1)$ showed up as an answer but I also got these ...
3
votes
1answer
43 views

Simplify multinomial trig expansion to fewer linear terms like Wolfram?

I'm mystified as to how Wolfram Alpha's TrigReduce[expr] does its magic, particularly on sums of long products that look like $$A \cos^a(B_1 x) \sin^b(B_2 x) \cos^c (B_3 x) \sin^d (B_4 x) \dots$$ I ...
2
votes
1answer
90 views

How to create animated plot of curve depending on parameter in WolframAlpha?

Is it possible to create in WolframAlpha an animated plot of a curve given by an equation, where some of the coefficients depend on the parameter (=on time)? For example if I would like to have a ...
2
votes
1answer
38 views

Change linear plot to 100% plot in Wolfram Alpha

Recently I have used this input for WolframAlpha: Plot (forumla1), (formula2), (formula3), {a, 0, 50} It's generating "Linear Plot" like on picture on left. Is ...
1
vote
1answer
34 views

Relations between hypergeometric functions

I am trying to find a relation between hypergeometrics $${}_2F_1(a,b,c;z)\,\,\text{and}\,\,{}_2F_1(a+1,b+1,c+1;z)$$ I can see that $$\frac{\partial}{\partial z}{}_2F_1(a,b,c;z) = ...
1
vote
1answer
65 views

is ${x^{2/3}}$ the same as ${\sqrt[3]{(x^2)}}$ or ${(\sqrt[3]x)^2}$? domain?

is ${x^{2/3}}$ the same as ${\sqrt[3]{x^2}}$ and ${(\sqrt[3]x)^2}$? and what is domain of $x$? Wolfram Alpha shows different results for ${x^{2/3}}$ and ${\sqrt[3]{x^2}}$ representations. Is domain ...
1
vote
1answer
69 views

Zeroes of the floor (greatest integer function)

I was just browsing Wolfram Alpha and looking at interesting graphs of functions when I noticed that it gave complex numbers for the numerical roots of $\lfloor x\rfloor$. Does anybody know why?
1
vote
1answer
236 views

How to do reduce rows with Wolfram Alpha over certain set

If I want to row reduce a matrix: $$ \begin{matrix} 1 & -1 & 0 & 4 \\ 2 & -2 & 1 & 3 \\ 5 & -5 & 1 & 15 \\ \end{matrix} $$ ...
1
vote
1answer
509 views

Newton backward interpolation in Mathematica

I have the following task: Create a function (in Wolfram Mathematica), called $\mathrm{NewtonBackward}$[n_,x0_,h_,f_] which interpolates backwards the function $f(x)$ with nodes {x_i = x_0 + ...
0
votes
1answer
59 views

What is the result of this infinite sum?

I'm trying to find the value of $\mathbf S$ where $$\mathbf S = \sum_{k=1}^\infty \frac{\sin(2\pi k x)}{k}; k \in \mathbb N, x \in \mathbb R^*$$ I had a look to WA which lead me to this result. I ...
0
votes
1answer
25 views

Plotting numbers in the complex plane using WolframAlpha

I read this article on understanding imaginary numbers as rotations of real numbers in the complex plane. Having read it, it's easy for me to see how the real number $1$ is simply a point on the real ...
0
votes
1answer
14 views

PrimeQ[ Table[sum_(n=1)^(N)n!, {N,1,30}]]

The PrimeQ[Table[...]] command used to work in Wolfram|Alpha back in 2012 but now it doesn't give any answer. Is there a substitute?
0
votes
1answer
106 views

Count of possible hands math + Python vs Wolfram Alpha

So I wanted to write a Python program to calculate some probabilities using hyper geometric distributions. However, I seem to get probabilities over 1 sometimes, so there must be something wrong with ...
0
votes
1answer
87 views

Finding vertex of a parabola -conflicting answers

For a given problem $g(x) = 5x^2 - 2x +1$, we were expected to describe the graph. WolframAlpha and I are finding conflicting issues. I do not think I made an approximation anywhere that would explain ...
6
votes
0answers
65 views

How wolfram defines injectivity?

I was looking for a fast way of getting which function is surjective and injective. So I tried to find such command in wolfram and surprisingly it says to me that $ln(x)$ is not injective. Link to ...
3
votes
0answers
55 views

Strange things on WolframAlpha: derivation, modulo and doubling result

I asked WA what is the derivative of $\frac1{\cos((x \bmod \pi/2)-\pi/4))}$ equal to for $x=0$. A very strange result came out. The exact result is $-\sqrt2 \mathsf{Mod}^{(1,0)}(0,\frac\pi2)$, ...
3
votes
0answers
1k views

How can I solve system of linear equations over finite fields in WolframAlpha?

Is it possible to solve system of linear equations over finite fields using Wolfram Alpha? If yes, how can I do that? Let us take a system $x+y+z=0$, $2x+y+2z=0$, $x+3y+z=0$. If I want to solve this ...
3
votes
0answers
241 views

How to Create a Lesson Plan with Wolfram Alpha

This will be my first post in this forum. I am so excited to see a lot of interesting posting from the community. From the FAQ, I learned that Mathematics stack exchange discussed about mathematical ...
1
vote
0answers
55 views

Maple and WolframAlpha return different results

I solved the integral of u/(1-u) by hand and found as result -ln(1-u) - u + constant. Now, when I evaluate this integral with WolframAlpha, I get the same result. But when I evaluate it with Maple, it ...
1
vote
0answers
32 views

Application of Initial Value Theorem

Let $$F(s):=\frac{s}{2s-i}$$ be the Laplace transform of some $f(t)$. I have been asked to compute $f(0^+)$ assuming that this quantity, intended as limit, exists. I thought I could apply the IVT ...
1
vote
0answers
97 views

A WolframAlpha error?

Consider the equation: $$ \dfrac{1}{\sqrt[3]{(x+3)^2}}-\dfrac{1}{\sqrt[3]{x^2}}=0 $$ that has the solution $x=\dfrac{-3}{2}$ as can be easely verified. But WolframAlpha gives no solutions (here). ...
1
vote
0answers
58 views

Fourier Tansform of derivative on Wolfram Alpha

If I'm not mistaken, the Fourier Transform of the $n$th order partial derivative of a function with respect to $x$, using the transform variable $k$ is: $$(i*k)^n * [F(k)]$$ so for the $1$st order ...
1
vote
0answers
80 views

Did Wolfram Alpha make this term up?

So I'm currently taking a Trigonometry class and I'm using the iOS version of the Wolfram-Alpha app to assist me with some of the more mundane calculations (Pythagorean Theorem, etc) and I've come ...
1
vote
0answers
29 views

radius of convergence of $1/\ln(in)$

I have series when $n$ goes from $1$ to infinity $(z/\ln(in))^n$ and need to find the radius of convregence. I tried this $1/R = \limsup ((1/\ln(in))^n)^(1/n)$ when $n \to \infty$ (Cauchy's rule), ...
1
vote
0answers
74 views

hypothesis test and execution? did I do this right?

I am trying to figure this out and I'm not sure if I am doing it right. a) did I select the correct type of hypothesis testing??? b) am I using the numbers in the right place (I have SD for 3.5 for ...
1
vote
0answers
124 views

Strange results for solving boundary angle of full reflection

I was trying to solve the following group of equations for $\alpha$ using Wolfram|Alpha: $$\frac{v_2\cdot\sin(\alpha)}{v_1} = 1 \\ v_1 > 0 \\ v_2 > 0$$ I expected something like $\alpha = ...
0
votes
0answers
11 views

Two variants of Radiality centrality

I am implementing Radiality centrality. For formula I am using definition from CentiScaPe: Network centralities for Cytoscape. I was doing some tests and I found some examples at Wolfram Alpha site. ...
0
votes
0answers
31 views

use of wolfram in determining area between two curves

I am new to the use of Wolfram (that for the limited cases I have used is very impressive). However I wonder if anyone can tell me what I am doing wrong. I wanted to calculate the area between the two ...
0
votes
0answers
27 views

Evaluating a sum on binomial coefficients

I'm reading Casella's and Berger's Statistical Inference. On page 239 they gives a claim that $$\sum_{x=0}^{330}\binom{300+x-1}x\left(\frac{1}{2}\right )^{300}\left (\frac{1}{2}\right )^x\approx ...
0
votes
0answers
12 views

Inserting “holes” on a graph.

I am trying to plot the set $A = \big\{(x,y) \in \mathbb{R}^{2} \mid x^{2} + y^{2} < 2 \big\} - \big\{(0,\frac{1}{n}) \mid n=1,2,3 \dots \big\}$. I have tried different combinations of set ...
0
votes
0answers
66 views

Solid has same volume when axis of rotation increases?

I'm working on calculating the volumes of different solids using integration. The problem I'm working on says to find the volume of two solids, one revolved around the line $x = 4$ and the other ...
0
votes
0answers
18 views

Plotting standard deviation function using WolframAlpha

I'm trying to plot a standard deviation function using WolframAlpha's function plotter and my function looks like this: $SD(Y) = \sqrt{\sum_{i=2}^{k}\frac{k(i-1)}{ (k-(i-1))^2 }}$ where k goes from 1 ...
0
votes
0answers
85 views

Plotting Dirichlet Series $L_{\tau}(s)$ related to Ramanujan tau function in Mathematica

According to wikipedia, Ramanujan tau function $\tau:\mathbb{N}\to\mathbb{Z}$ is defined by equating the coefficients of the power series on both sides of the identity: ...
-1
votes
0answers
18 views

Fourier series of a piecewise function

Over period $-3\lt t \lt 3$ $f(t) = \begin{cases} 2, & {-3\lt t \lt 0} \\ 0, & {0 \lt t \lt 3} \end{cases}$ Can the above be entered in WolframAlpha? I want to check my answer