For questions related to usage of Wolfram Alpha.

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1
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3answers
84 views

Why is Wolfram Alpha miscomputing this problem? [on hold]

I was incorporating Wolfram Alpha into an API I am build, and to test it entered a few equations. One of the equations I entered was as follows. !6/(!3*!3) This ...
5
votes
1answer
109 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 ...
0
votes
0answers
14 views

Discrete Fourier Transform using WolframAlpha

I tried to verify a calculation with WolframAlpha. I want to compute the DFT of $[2,3,-3,1]$. So in particular one entry of the result vector should be $2+3-3+1=3$. I don't understand why I get ...
6
votes
1answer
932 views

How do I plot multi case function in wolfram or geogebra?

How do I plot the following multi case function in wolfram or geogebra? $$ \begin{eqnarray*} f(x) = \begin{cases} 1, &\text{if }x \text{ is an integer}, \\ 0, &\text{if }x \text{ is ...
0
votes
2answers
680 views

How to solve this graph problem in WolframAlpha?

I need to input this problem in WolframAlpha: Write an equation of the line containing the given point and parallel to the given line: $(8,-8)$, $7x+8y=5$. The answer is $7x+8y=-8$ but I'm not ...
0
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2answers
74 views

Simplifying fractional exponents

I am very confused about the following: whenever I put in into wolfram alpha the answer it gives me is "indeterminate", is it not possible to simplify fractional exponents or something? if the ...
1
vote
1answer
347 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 + ...
4
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2answers
90 views

Different results when integrating 1/(x^2-9) with computer tools

For checking my calculations, I generally use Wolfram Alpha or a similar tool. Today, I wanted to check the following integral: $$\int {\frac{1}{{9 - {x^2}}}} dx$$ From my calculations, using ...
1
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0answers
33 views

Fourier Tansform of derivative on Wolfram Alpha

If I'm not mistaken, the Fourier Transform of the nth order partial derivative of a function with respect to x, using the transform variable k is: (i*k)^n * [F(k)] so for the 1st order derivative ...
4
votes
2answers
57 views

Regarding $\lim \limits_{(x,y,z)\to (0,0,0)}\left(\frac{x^2z}{x^2+y^2+16z^2}\right)$--is WolframAlpha incorrect?

$$ \lim_{x,y,z\to 0} {zx^2\over x^2+y^2+16z^2}$$ So I am trying to evaluate this limit.. To me, by using the squeeze theorem, it seems that the answer must be zero. I trying using the ...
0
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2answers
55 views

Wolfram alpha integral

I want to evaluate the following integral in woflram alpha int[x e^(-lambda*(x-v)),{x,v,infinity} ] It doesn't work for some reason. It does work when instead of v, I put a number. For example ...
2
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2answers
52 views

What is the difference between $\ln(\sin\frac{x}{2}+\cos\frac{x}{2} )- \ln(\sin\frac{x}{2}-\cos\frac{x}{2})$ and $\ln(\tan x+\sec x)$

I've noticed if you ask wolfram what is the integral of $ \sec x$ they will answer $$\ln\left(\sin\frac{x}{2}+\cos\frac{x}{2}\right) - \ln\left(\sin\frac{x}{2}-\cos\frac{x}{2}\right)$$ I've been ...
0
votes
0answers
38 views

Multiple sums or products in wolfram-alpha

How can I compute something like $$\prod_i^n \prod_j^m ij$$ in wolframalpha? (for finite n and m) I have tried a great number of combinations that have only resulted in failure.
15
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2answers
45k views

How to type logarithms in Wolfram|Alpha?

Its sometimes hard to type it if logarithm is not natural and base is not 10, especially if base is variable. So anyone know rules how to type?
2
votes
2answers
67 views

Wolfram Alpha result for infinite series summation .

Consider the infinite sum $s=1+1/2^2-1/3^2-1/4^2+1/5^2+1/6^2-...$. We can see that the series is absolutely convergent and hence convergent. But WolframAlpha seems to give me a different answer. When ...
0
votes
1answer
72 views

Recurrence Equation Solution / Difference equation - WolframAlpha

I am given the recurrece equation $y_k-7y_{k-1}=5^k$ and found the (hopefully correct) particular solution to be $y_k^P=-\frac{5}{2}5^k$ WolframAlpha, however, gives the particular solution ...
1
vote
2answers
98 views

Can wolframAlpha be wrong on this vector limit?

We had a homework on multivariable analysis, and there was this problem and the teacher said that we didnt trust wolfram but I'm not convinced on it, because of this. Is ...
1
vote
2answers
31 views

Handedness in Quaternion multiplication

I've received some code (which I didn't write) and decided at some point to write test cases for the Quaternion math implementation. I used Wolfram alpha to get the result q1 * q2, where: q1 = (4.0 ...
1
vote
0answers
27 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
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1answer
37 views

Solve for Y; don't understand Wolfram Alpha's solution

Answering this StackOverflow question, I needed to solve this equation in terms of y: $$x = 6.1 + \log(\frac{{y}}{{0.03p}})$$ Doing it by hand: $$y = 0.03p10^{{(x-6.1)}}$$ Wolfram alpha tells me ...
1
vote
2answers
88 views

Name of special function used by Wolfram integrator

Integrating $e^{-r}/\sqrt{2t-r}$ with respect to $r$ between $r=t$ and $r=2t$ using this widget gives the answer $2e^{-t}F(\sqrt{t})$. However the widget doesn't say what $F$ is. I have looked on ...
6
votes
2answers
78 views

Calculate with sequences from OEIS

Is there any easy way to do calculations with sequences from OEIS online? For example I would like to input something like: (A007620(n+1) / 2 ) + A000027(n) and ...
0
votes
2answers
57 views

What are the limitations of modelling a piano sound with the 'play' option of the software Wolfram Mathematica?

'Play' is an input availabe on Wolfram mathematica, which shows how a wave would sound and I am asking myself what the limitations of this input are, in what aspects it does not represent 'real' sound ...
0
votes
1answer
48 views

stuck with a cubic equation

I picked an equation $0= x^3 +x^2 -2x -1$ I plotted it with geogebra, to see if it had more than $1$ real root. It definitely cuts the $x$-axis $3$ times. But when I checked wolfram alpha, to see ...
1
vote
2answers
233 views

Evaluation of the integral $\int_{-6}^{-3}\frac{\sqrt{x^2-9}}{x}$

How to evaluate the following integral? I have tried the following things but I have no idea to continue after the last step. Moverover, the integral seems wrong when compared with the ans from ...
3
votes
2answers
53 views

Real integral getting numerically evalued to complex number

I tried feeding th following integral into WolframAlpha: $$\int_0^2\frac{1}{3\sqrt{x}(\log(x))^{\frac13}},$$ to get an idea of its value. Result: http://bit.ly/strangeint ...
10
votes
2answers
197 views

Proof that cos(1) is transcendental?

So, I was playing around on Wolfram|Alpha (as we nerds like to do) and it said cos(1) was transcendental. Could someone provide me with the proof that cos(1) is transcendental?
7
votes
5answers
102 views

$\sec\theta$ never equals $\tan\theta$. Or does it?!?

Wolfram-alpha is disagreeing with me. I am wondering why: which of us is wrong? I was writing a question to demonstrate why domains of functions matter. The question is: Does there exist an angle ...
1
vote
1answer
66 views

Wolfram interpretation of arccot(x)

I was calculating a $$\lim_{{x \to -\infty}}\left(\frac{4-x}{1-x}\right)^{2x\mathrm{arccot}(x)}$$ and found a problem og how wolframalpha presents $\mathrm{arccot}(x)$. I was taughted that plot of ...
2
votes
3answers
88 views

Wolfram alpha error in global minimization?

Let us consider the function $$f(x,y)= x + y^2 - \ln(x+y)$$ If you try to minimize it using Wolfram Alpha (http://www.wolframalpha.com/input/?i=minimize+x%2By%5E2-ln%28x%2By%29), it founds a local ...
3
votes
2answers
899 views

limit of $2^n/3^{n/2}$ as $n\to\infty$

$$ \lim\limits_{n\to\infty}\frac{2^n}{3^{\frac{n}{2}}}$$ I used wolfram to get the limit as follows: "lim n tends infinity 2^n/3^(n/2)". And using L'Hospital's rule the result was: ...
7
votes
3answers
771 views

Integration substitution: How does Wolfram Alpha come up with this step?

I have to integrate $$ \int \frac{1}{(\sin x) (\cos x)} \, dx $$ I looked at the Wolfram Alpha step by step solution to figure out how to do it. First, it rewrites the integral as: $$ \int (\csc ...
0
votes
1answer
386 views

How to solve this linear set of equations using W|A?

I try to solve a simple system of four linear equations in the variables ch1, ch2, co1 and co2: ...
3
votes
1answer
34 views

Curvature of plane curve, formula disagrees with Mathematica?

I have the following equation $$y=\pi\ln(2x)$$ And when I ask Mathematica/WolframAlpha for the curvature I get $$K=\frac{\pi x}{(x^2+\pi^2)^{3/2}}$$ However the formula for curvature of a plane ...
4
votes
3answers
106 views

How does Wolfram Alpha come up with the substitution $x = 2\sin u$? Integration/Analysis

I have to integrate $$ \int_0^2 \sqrt{4-x^2} \, dx $$ I looked at the Wolfram Alpha step by step solution, and first thing it does is it substitutes $x = 2\sin(u)\text{ and } \,dx = 2\cos(u)\,du$ ...
1
vote
1answer
83 views

Torricelli's Law with a Sphere (Ignore Mathematica part, already solved)

Edit 1: According to this PDF, second page. The differential equation for a hemisphere becomes $$(r^2h-h^2) h' = -a^2\sqrt{2gh}$$ This differs from the equation I got, which looks like: ...
0
votes
1answer
28 views

Laplace Transform of $e^t\cos(3t)\operatorname{heaviside}(t)$

Find the Laplace Transform of $e^t \cos(3t) \operatorname{heaviside}(t)$ Since $\operatorname{heaviside}(t)g(t) = \mathcal{L}(g(t)) $ and $\mathcal{L}(e^t\cos(3t)) = \frac{(s-1)}{(s-1)^2+9} $ ...
2
votes
2answers
75 views

compute exponential of matrix with wolfram alpha

I would like to use wolfram alpha to compute matrix exponential. I have tried with the exponential of the identity matrix, with this input: exp({{1,0},{0,1}}) But what I get is unexpected. The ...
0
votes
1answer
42 views

Solution to h'(t) = h(t)^j : Wolfram Alpha mistake?

This should be a quick and easy one. Trying to teach myself a bit more about differential equations, so I put the following equation into Wolfram Alpha: $$h'(t) = h(t)^j$$ It gave me the following ...
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2answers
45 views

Solve system of equations

Are there any good resources for solving systems of equations out there? I tried to put this into wolfram alpha, but it doesn´t seem to work: ...
1
vote
1answer
42 views

Evaluating a decimal exponent

The example I am stuck with is $(-1)^.456$. According to my calculator, the answer is -1. According to WolframAlpha and the Google Calculator, it is a complex number. WolframAlpha -- ...
0
votes
3answers
424 views

Is Wolfram Alpha wrong with a simple derivative?

Let $f=\frac{x^2w(y-z)t}{18l}$ then (imho): $\frac{\partial{f(x,y,z)}}{\partial{w}}=\frac{x^2t(y-z)}{18l}$ However Wolfram Alpha produces a quite different result: Wolfram alpha result ...
1
vote
0answers
63 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 ...
0
votes
1answer
272 views

how to substitute a variable by a number in wolframalpha

Peace be upon you, How can I compute \begin{align*} sin'(0) \end{align*} in Wolframalpha? like what in Maple, I try subs(diff(sin(x),x),x=0) But it doesn't ...
0
votes
1answer
72 views

How can the integral of $|\sin(x)|$ be $-\cos(x)\text{sgn}(\sin(x))$?

Wolfram|Alpha tells me that $\int|\sin(x)| = -\cos(x)\text{sgn}(\sin(x))$ (which happens to also be its derivative), but I don't understand how this is possible, because the resulting function jumps ...
0
votes
0answers
41 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: ...
0
votes
2answers
40 views

How do I get wolfram to solve this problem?

I am trying to check some answers and can't seem to get wolfram to work properly. I type in the following command : integrate x.sin(x) dx and it doesn't provide any solution it just says "visual ...
1
vote
1answer
106 views

Is there any way how I can use Mathematica in Introduction Logic course?

I am very new comer to Wolfram Mathematica software tool and I am interesting is there any way how I can apply this tool for Introductory Logic course. I am participating at the course on 'coursera' ...
1
vote
1answer
64 views

Analytic solution for the ODE $\frac{d y(x)}{dx}=\frac{a*y(x)^3+b}{c* y(x)^3+ d}$

I have an ODE $$ \frac{d y(x)}{dx}=\frac{a*y(x)^3+b}{c* y(x)^3+ d},$$ where $a,b,c,d$ are constants, and I would love to solve it analytically. I tried Maple 15 and 17 and got $$ y \left( x \right) ...
0
votes
0answers
138 views

Why is Wolfram Alpha wrong?

I calculated $$\tan 75^o - [\cos 13^o\cdot \cot 23^o \cdot \tan 31^o \cdot \tan 35^o\cdot \tan41^o]$$ and I got a nonzero answer: ...