For questions related to usage of Wolfram Alpha.

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2
votes
3answers
600 views

WolframAlpha blows simple substitution?

I am to find a formula for the n-th derivative of $$\frac{1+x}{1-x}$$ I came up with $$\frac{(-1)^{n+1} \times 2 \times n!}{(1-x)^{n+1}}$$ This seems right, but I noticed that WolframAlpha somehow ...
0
votes
1answer
383 views

How to calculate vertices of dodecahedron using W|A?

Can I calculate for example with wolfram alpha coordinates of vertices of dodecahedron? I know coordinates of center point of dodecahedron (center of gravity) and the height of dodecahedron. Thanks ...
2
votes
1answer
281 views

Is wolframalpha a good nonlinear optimization tool? [closed]

Also how do you restrict the domain to be integers in wolfram alpha?
0
votes
3answers
206 views

Why doesn't WolframAlpha factor my equation?

I entered in a simple-looking quadratic equation, expecting WA to factorize it for me, but then it gives me all this other stuff without the actual factors. The result is exactly the same as my input. ...
1
vote
2answers
3k views

Why does Wolfram Alpha handle $\log$ and $\ln$ the same?

I thought $\log(n)$ was like $100^x = n$ and $\ln(n)$ was $e^x = n$. But when I do $\ln(80)$, it gives me the answer for $\log$. Why is that?
0
votes
1answer
12k views

Taylor series expansion of arctan(x) around the point 0

This is actually a technical question about why I'm getting different results when trying to do the same thing using Maxima and WolframAlpha. When I enter expand arctan(x) in WolframAlpha I ...
0
votes
1answer
394 views

Priority of parentheses and brackets in basic arithmetic.

Wolfram alpha is giving inconsistent results to this problem: When I enter: 16÷2( 8-3(4-2) )+1 the result is 17. When I enter: 16÷2[ 8-3(4-2) ]+1 the result is 5. and 16÷2*[ 8-3(4-2) ]+1 brings ...
1
vote
1answer
836 views

Set of modular equations in Wolfram|Alpha

Am I able to solve set of modular equations in Wolfram|Alpha, like for example: $ \left\{\begin{matrix} x \equiv 2 \pmod{3} \\ x \equiv 3 \pmod{5} \end{matrix}\right. $ ?
1
vote
1answer
107 views

An integral evaluation

I tried my luck with Wolfram Alpha, with $p \in \mathbb{R}$ $$\int_{-\infty}^{\infty} \frac{x^p}{1+x^2} dx = \frac{1}{2} \pi ((-1)^p+1) \sec(\frac{\pi p}{2})$$ for $-1<p<1$, and doesn't exist ...
0
votes
1answer
114 views

Help me with this mock-long-division $\frac{-x+2}{x^{2}+x-2}=\frac{-4}{3(x+2)}+\frac{1}{3(x-1)}$

$$\frac{-x+2}{x^{2}+x-2}=\frac{-4}{3(x+2)}+\frac{1}{3(x-1)}$$ Wolphram Alpha states that one can do this with long division, I cannot immediately realize it. Could someone show the trick to simplify ...
1
vote
1answer
170 views

p-norm of series / Mathematica

When computing the $p$-norm of the series $x_n = \mathrm e^{\mathrm i n}$ for $n \in \mathbb{Z}$ (not $\mathbb{N}$), the sum should not converge: $$\|x\|_p^p = \sum_{n \in \mathbb{Z}} (\mathrm ...
1
vote
2answers
248 views

Graph of a Log Function

I am curious as to why Wolfram|Alpha is graphing a logarithm the way that it is. I was always taught that a graph of a basic logarithm function $\log{x}$ should look like this: However, ...
2
votes
1answer
2k views

How to type logical expressions in WolframAlpha?

Usually WolframAlpha understands what logical expression I have entered but sometimes I can't find a way to do it especially when you are using equivalent sign. For example if I have $$ p \land q ...
10
votes
1answer
595 views

How would you input xkcd.com/287 into WolframAlpha?

In this XKCD comic, a stick figure asks an NP-complete problem to order exactly 15.05 worth of appetizers out of a menu that includes the following list of prices: ...
2
votes
2answers
12k views

Using Wolfram Alpha For Solving A System Of Equations

How do i input the below system of equations in wolfram alpha in order to solve for the unknowns and plot them? If i just say "solve" and input these equations one after the other with a simicolen ...
3
votes
3answers
2k views

Using Wolfram Alpha to output table of values over the integers

I'm trying to get Wolfram Alpha to output a table of values over the integers for a given function, in example: n^2-n 1----1 4----2 9----3 ... ... (using '-'s instead of ...
1
vote
1answer
178 views

How to graph a cumulative subtraction on Wolfram Alpha

I'd like to graph a timing algorithm that I'd been using (that did essentially the opposite of what I wanted). I apologize if I'm not using the correct name to refer to it. Essentially it was timer = ...
0
votes
2answers
503 views

Have I found a bug in Wolfram Alpha's Partial Derivative Solver?

I was using This Wolfram Alpha Page to calculate the partial derivatives of the sum of two gaussians. It believes the answer to be: $$ e^{-(b-x)^2/2 c^2} $$ but the working shows it as ending on: ...
0
votes
2answers
671 views

a question about the sum of $ e^{ikx}$

I have a simple question. Let $ S = \sum\limits_{k = 1}^n {e^{ikx} } $ using the typical trick , we also have $ S\left( {e^{ix} - 1} \right) = e^{i\left( {n + 1} \right)x} - e^{ix} $ and if $ ...
6
votes
1answer
660 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
1answer
218 views

Problems Using Wolfram Alpha

I've always had some problem with the usage of wolfram alpha.It computes simple derivates, integrals and solves simple linear and quadratic equations flawlessly.It seems to me that it ignores step by ...
0
votes
1answer
193 views

Understanding a Wolfram|Alpha explanation on a simple integral

I'll probably kick myself when someone explains it, but I can't understand where the 1/12 comes from after the re-substitution of u? I thought it would be 1/3, but it clearly isn't. Why is that? ...
0
votes
1answer
11k views

Use WolframAlpha to compute the real Fourier series of a function

How can I use Wolfram|Alpha to compute the Fourier series (with real coefficients $a_0, a_n$ and $b_n$)? (The 'Fourier series' command seems to summon the complex series) I.e. $f(x) = x + \pi$ for ...
8
votes
1answer
2k views

variable bounds on definite integrals in Wolfram|Alpha

I often have trouble getting Wolfram|Alpha to compute definite integrals with variable bounds, and I'm wondering whether I'm missing something. Some examples: $\int_a^b \sin x\mathrm dx$ and $\int ...
2
votes
0answers
189 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 ...
3
votes
1answer
636 views

Is Wolfram Alpha Wrong? (LU Decomposition)

Ok, I've been working on a matrix solver for a while (no, its not going well, thanks for asking), and just discovered something that worrys me alot; The problem at hand is LU Decomposition of a ...
8
votes
2answers
22k 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
654 views

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

$$ \lim_{n\to\infty}\frac{2^n}{3^{n/2}}$$ 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: ...
12
votes
2answers
326 views

What is the meaning of a number's “representation” on Wolfram Alpha?

When searching a number on Wolfram Alpha, one of the results is its representation. For example, for 8549: 8549 has the representation 8549 = $5·2^6·3^3-91$. Similarly for 75290: ...
2
votes
2answers
632 views

Comparing integral resolutions using Wolfram Alpha / Mathematica

Equations are in $\LaTeX$ format; I'm still trying to understand how MathJax works. Given the following integral: $\int_0^{+\infty } \frac{1}{x \sqrt{x}} \, dx$ I'm pretty sure that does not ...
0
votes
2answers
218 views

$f(x) = f(x-1)*b \to f(x) = c_1 b^{x-1}$

I'm trying to teach myself mathematics. I only started last year with a previous knowledge of basic arithmetic. I often make a detour into regions featuring problems that are a bit too deep for me. ...
1
vote
1answer
365 views

WolframAlpha Returns only 2 Roots for a Polynomial Equation of 6 Degree

I think this is really weird. I want to solve the following equation: $$(2x^2+3x+5)^3+(2x^2+3x+5)^2=0$$ This is a polynomial equation of 6 degrees. It should have 6 roots. But wolframalpha only ...
2
votes
2answers
1k views

Wolfram Alpha: How to show functions with abs() and sgn() as a piecewise function?

I was trying to obtain this result: integrate e^|x| dx The result is $$ \int e^{|x|} dx = \frac12 e^{-x} \left( (e^x-1)^2 \operatorname{sgn}(x) -2e^x +e^{2x} - ...