For questions related to usage of Wolfram Alpha.

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2answers
58 views

Wolfram Alpha “x = derivative x”

Asking Wolfram Alpha $x = \text{derivative } x$, I was expecting $e^x$, being that the derivative of $e^x$ is $e^x$, Wolfram Alpha however yields $x = 1$. Is this stating that the derivative of a ...
2
votes
3answers
105 views

Did Wolfram|Alpha mess up $\int 1 - \frac{1}{1-e^{-x}} \mathrm{d}x$ or did I?

I want to calculate $$\int 1 - \frac{1}{1-e^{-x}} \mathrm{d}x$$ Provided that $x>0$. Substituting $u=1-e^{-x}$, we get: $$\int \frac{1 - \frac{1}{u}}{1-u} \mathrm{d}u = -\int \frac{1 - ...
-1
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1answer
52 views

Code Wolfram Mathematica [closed]

Sorry but I do not know English very well. The question is very simple, I hope someone knows the code that makes my case. In fact, writing: ...
2
votes
2answers
104 views

How does WolframAlpha solve quintic equations (5th degree polynomials)?

There exists no general formula for quintic equations. Then how does WolframAlpha solve quintic or higher degree polynomial. Is there a sure way to get values of roots of quintic or higher degree ...
3
votes
1answer
35 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 ...
-3
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2answers
73 views

Wolfram Alpha formula not working [closed]

I'm trying to solve the following formula for X in Wolfram but when I input it I get an error saying it does not understand "solve". $0 = ...
0
votes
1answer
68 views

Why can't Wolfram calculate the Laplace transform of $\sinh(t)\sin(t)$ correctly?

Question Show that the Laplace transform of $\sinh(t)\sin(t) = \frac{2s}{s^4+4}$. Wolfram can't calculate this as is, so I tried to simplify it a bit. I defined $\sinh(t)$ as $e^t-e^{-t}$ and split ...
3
votes
2answers
63 views

Plot of $y=x+0\sqrt{-x}$ (and WolframAlpha vs Desmos)

To plot the graph of $y=x+0\sqrt{-x}$ : Do we have to first find out the domain of $y$ which is $y \in ( -\infty,0 ]$ ? $\color{blue}{\text{[Case 1]}}$ (that's what I do) Or do we solve the ...
2
votes
2answers
83 views

Is Wolfram-Alpha giving me a wrong result?

I have to calculate: $$\nabla^2 \frac{e^{ikr}}{r}$$ which I know to be $\displaystyle -k^2 \frac{e^{ikr}}{r} $ (from a lecture). Doing it by hand: $$ \nabla^2 f(r) = \frac{1}{r^2} ...
1
vote
4answers
144 views

Is Wolfram Alpha calculating this incorrectly?

I entered in "does $2ln(x)$ equal $ln(x^2)$" into Wolfram and it came out false. Purplemath.com says that $log_b(m^n) = n · log_b(m)$. Which is correct? And why is there a difference?
3
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2answers
568 views

The sum of digits of $3(3x+3)$ is always $9$ for any $x$ between $1$ and $9$

Given the following 'joke' I stumbled across today It's easy enough to figure out that the answer is always 9. Asshole. However when I tried to 'prove' this for ...
0
votes
2answers
47 views

How to do multiplication (capital pi) in WolframAlpha?

How do i ask this in WolframAlpha: $$\prod_{i=0}^{i=10} \sin{(i)}$$ I used $\text{product}(...)$ and $\text{multiply}(...)$ or even $\text{multiplication}(...)$ but they don't seem to work. I am ...
0
votes
1answer
43 views

What function does Wolfram Alpha plot instead of the factorial?

Look to the second graph where Wolfram Alpha gives a continuous factorial function: What is the second graph? It is not the gamma function, since that has $\Gamma(-1)=0!=1$.
0
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3answers
93 views

WolframAlpha wrong(?) graph

I had a question to plot a graph of $\space \space\LARGE y=x^{x^{x^{x^{...}}}}$ Which (according to me) is equivalent to $\large y=x^y \Rightarrow y^{\frac{1}{y}}=x$ So i plotted them in ...
14
votes
7answers
2k views

Conflicting limit answers using calculator and wolfram alpha

I want to evaluate $\lim\limits_{x\to0} \dfrac{\tan(x) - \sin(x)}{(\sin(x))^3}$, Calculator says it's 0 when substituted with 0.0000000001. Wolfram Alpha says it's 1/2. The Problem Set says the ...
3
votes
2answers
146 views

Solving $\frac{dx}{dt} = A \frac{ (1-x)}{(t-t^2)} - \frac{(B*x -C*x^2)}{(t-t^2 )*(t-x)}$ (using wolfram/mathematica)

I would like to solve the following non-linear ordinary differential equation: $$\frac{dx}{dt} = A \frac{ (1-x)}{(t-t^2)} - \frac{(B*x -C*x^2)}{(t-t^2 )*(t-x)}$$ -I need an analytic solution. -I ...
1
vote
2answers
50 views

Wolfram alpha giving wrong result on recurrence?

I have the recurrence$$a_{n+2}-a_n=1$$ The answer I got was $a_n=A+B(-1)^n+\frac n 2$, while WolframAlpha is giving me $a_n=A+B(-1)^n+\frac n 2- \frac 1 4$. Although when I plug them in the ...
1
vote
3answers
272 views

Why does Wolfram Alpha say that $n/0$ is complex infinity?

I typed a number divided by 0 on Wolfram Alpha and thought that it would say "undefined". However, when I pressed enter it told me that the answer is complex infinity. I have always been taught ...
2
votes
1answer
53 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
2answers
63 views

For what values of k is this singular matrix diagonalizable?

So the matrix is the following: \begin{bmatrix} 1 &1 &k \\ 1&1 &k \\ 1&1 &k \end{bmatrix} I've found the eigan values which are $0$ with an algebraic multiplicity of $2$ ...
0
votes
1answer
34 views

Plotting graph in Wolfram Mathmatica?

Which is the function that can plot me the graph K 7, 2 in mathematica? And after that to delete 2 edges?? Thanks for the help.
2
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1answer
34 views

How to find cubic residues $\bmod p$ using WolframAlpha?

How to find cubic residues $\bmod p$ using WolframAlpha? Just type in "quadratic residues modulo p" and you're done, but typing in "cubic residues modulo p" does nothing. Logically, "x^3 ...
1
vote
3answers
100 views

Why is Wolfram Alpha miscomputing this problem? [closed]

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 ...
0
votes
1answer
80 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 ...
4
votes
2answers
101 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 ...
4
votes
2answers
64 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
votes
2answers
75 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
votes
2answers
57 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 ...
1
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0answers
42 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 ...
2
votes
2answers
93 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
89 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
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2answers
113 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
72 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
1answer
44 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
1answer
81 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 ...
3
votes
2answers
58 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 ...
7
votes
5answers
120 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 ...
2
votes
1answer
89 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
104 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
1answer
42 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 ...
5
votes
3answers
115 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
109 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: ...
7
votes
3answers
832 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
39 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
173 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
46 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 ...
0
votes
2answers
48 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
129 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 -- ...
1
vote
0answers
72 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
1answer
576 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 ...