For questions related to usage of Wolfram Alpha.

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4answers
2k views

Wolframalpha - how to get value of function in a specific point?

For example , given this function - $f(x) = x^3-x^2-x-1$ and I want to check it in the point $x=1.6$. What should I have to write in the command line of wolframalpha in order to get it ?
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3answers
112 views

Generating function with quadratic coefficients.

$h_k=2k^2+2k+1$. I need the generating function $$G(x)=h_0+h_1x+\dots+h_kx^k+\dots$$ I do not have to simplify this, yet I'd really like to know how Wolfram computed this sum as ...
0
votes
1answer
435 views

How to calculate vector * matrix-inversed in Wolfram Alpha?

I am trying to calculate the product of a vector and an inversed matrix in wolfram alpha: $\begin{bmatrix}1 & 2 & 3\end{bmatrix}$ * $\begin{bmatrix} -0.5 & 0 & 0 \\ 3 & 1 & 0 ...
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1answer
355 views

Getting weird integral evaluation from Wolfram Alpha

Check this out. I hand-evaluated this integral and my pretty sure the answer is zero, but Wolfram returns the value $4i\pi$ instead.
0
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1answer
47 views

Permutations - bug in Wolfram Alpha?

I've got question whether Wolfram Alpha has bug in showing permutations. Check permutation rules, list, and two-line notation in this permutation. I'd expect same result as was on Wolfram Alpha blog ...
1
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2answers
591 views

Wolframalpha step-by-step of $\int\frac{\cos(x)}{\sqrt{2+\cos(2x)}}dx$

I wonder, where the minus sign goes after the first $u$-substitution of integral $\displaystyle\int\frac{\cos(x)}{\sqrt{2+\cos(2x)}}dx$?
6
votes
4answers
485 views

Why WolframAlpha Result is Different?

http://www.wolframalpha.com/input/?i=x%3D10%5E-15%3B+%28e%5Ex-1%29%2Fx When i click Approximate Form in result, the result is: ...
4
votes
5answers
868 views

Find the second derivative of $e^{x^{3}}+7x$

$$e^{x^{3}}+7x$$ Here is what I have tried so far, $$y'=(e^{x^{3}})'+(7x)'$$ $$y'=3e^{x^{2}}e^x+7$$ $$y'=3e^{x^{3}+x}+7$$ I am supposed to find the second derivative but I believe I have already made ...
0
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2answers
4k views

How to enter subscript characters in WolframAlpha? [closed]

I'm trying to enter equations like this in WolframAlpha. How do I format this?
0
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1answer
165 views

Equation with 2 variables tricky problem

So let's say I have some random equation $6yx^3 - 3yx + 5 = 0$, but could be anything. How would I go about finding a value for $y$, that makes it so that this equation only holds true if $x$ is ...
16
votes
4answers
1k views

Wrong Wolfram|Alpha limit?

I have this function: $$ f(x,y) = \frac {xy}{|x|+|y|} $$ And I want to evaluate it's limit when $$ (x,y) \to (0,0)$$ My guess is that it tends to zero. So, by definition, if: $$ \forall \varepsilon ...
6
votes
3answers
2k views

Derivative of floor function

I thought the derivative of function $\text{floor}(x)$ should be $\infty$ for integer values of $x$ and 0 elsewhere. But wolframalpha plot showed something different. Is there any explanation?
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2answers
7k views

Wolfram Alpha: How to define constants in a system of equations?

I'd like to use WA to solve a small system of nonlinear equations, that involve both constants and the variables of interest. How do I "tell" WA which variables are the constants, and which are the ...
1
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1answer
308 views

Moving the negative out of the integral - a bug in Wolfram Alpha?

A guy I follow on Twitter seems to be having some issues with Wolfram Alpha - namely that moving a negative outside of an integral results in two different answers: $\int -f(x) = -\int f(x)$ gives ...
26
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4answers
1k views

A limit wrong using Wolfram Alpha

I want to calculate the following limit: $$\displaystyle{\lim_{x \to 0} \cfrac{\displaystyle{\int_1^{x^2+1} \cfrac{e^{-t}}{t} \; dt}}{3x^2}}$$ For that, I use L'Hopital and the Fundamental Theorem ...
0
votes
1answer
35 views

How to calculate HarmonicNumber(x, 1.6)?

I got this solution while using Wolframalpha: $$ (-1.66667 n+1/2-0.133333/n+0.0208/n^3-0.0127573/n^5+O((1/n)^6))/n^1.6+2.28577 $$ Could somebody tell me this solution step-by-step? I need to write ...
0
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1answer
797 views

WolframAlfa/Mathematica how to find function local maximum on interval

I have a polynomial function and i want to find it's minimum and maximum on a the interval [0, 5] with Wolfram Alphaa but i forgot the proper input. I recall it went something like so: $x^4 + x^3 + ...
5
votes
4answers
157 views

Should $x=-2$ be included as an answer for $\frac{x^2+8x+12}{x^2+5x+6}>0$?

$$\frac{x^2+8x+12}{x^2+5x+6}>0$$ First of all while solving inequalities I need to check domain so in this case $$x^2+5x+6\neq0$$ $$x\neq-2,\ x\neq-3$$ Later on ...
2
votes
1answer
334 views

Circumference of the ellipse, elliptic integrals, and WolframAlpha

The arc length of a graph of a function $f(x)$ is $$\mathcal{l} = \int_a^b \sqrt {1 + f'(x)^2} dx$$ If you choose $f$ to be a parametrization of the ellipse with $a=1, b=\frac{1}{2}$, i.e. $f(x) = ...
1
vote
1answer
575 views

Wolfram|Alpha Plotting multiple geometric objects

I am trying to use WoflramAlpha to plot several gemoetries at once. It works fine up to an extent but after I add three different geometries to draw it just says it doesn't understand and picks ...
2
votes
2answers
164 views

(Wolframalpha) this shouldnt give x=50?

This is my problem: I need x or y for the triangle area that forms between the vertical axis(y) and the function y=100+2x where the area is equal to 2500. so I used for condition to the linear ...
7
votes
1answer
666 views

Wrong Wolfram alpha result?

I have this function $$ f(x,y) = \left\{ \begin{array}{ll} \frac{x^3}{x^2 + y^2} & \mbox{if } (x,y) \neq (0,0) \\ 0 & \mbox{if } (x,y) = (0,0) \end{array} \right. $$ And I want to ...
25
votes
1answer
356 views

Iterated exponent of $i$

WolframAlpha seems to tell me that $e^{e^{e^{e^{e^{e^{e^{e^{e^{e^{e^i}}}}}}}}}} = 1$, see link. Is this just an error or is it for real? Adding one more $e$ to the bottom of the tower gives me the ...
3
votes
1answer
269 views

How can I construct a 2^63-gon with a straightedge and compass?

I entered 2^63 as a stand alone value at WolframAlpha. Among the responses was a factoid that 'A regular 9223372036854775808-gon is constructible with a straightedge and compass.' What is such a ...
0
votes
1answer
60 views

Confusion in the answers given by mathematica

When I typed in 6^-1 mod 49 in Wolfram|Alpha, it gave me an answer of 41. Link here If I type the same thing as (1/6) mod 49 , I don't see 41 any more. Why is this happening ?Link here A ...
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1answer
397 views

How to plot and shade on Wolfram Alpha?

Many Mathematica parameters don't work on Wolfram Alpha. I tried filling -> f which it does not recognize. I am trying to plot a simple region bounded by $y = ...
4
votes
2answers
137 views

Is $2^{\log_2(-5)}$ defined?

As far as I know for $\log_2 x$ to be defined $x$ must be higher than 0. However when I enter $2^{\log_2(-5)}$ into wolframalpha it gives result $-5$. Is it mistake?
4
votes
1answer
5k views

Contour integration and wolfram

I am not sure if this is the right site to ask this question, but here it is: Does Wolfram Alpha do contour integrals? If so how might I access that feature. Also, is there an online manual for ...
1
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1answer
114 views

Question on y axis of Gamma probability distribution

Afternoon. I'm looking into using the Gamma (Erlang) distribution for a certain quantity that I need to model. I noticed by plugging in some values for the distribution parameters that the y axis ...
1
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1answer
81 views

Trivial transfiguration

I have $\frac{2ab}{ab-ac-bc+c^2}$. Of course it's $\frac{2ab}{c^2-ac-bc+ab}$ which is $\frac{2ab}{c^2-c(a+b)+ab}$ but for the latter Wolfram tells me it's not the same as $\frac{2ab}{ab-ac-bc+c^2}$. ...
2
votes
3answers
647 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
462 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
314 views

Is wolframalpha a good nonlinear optimization tool? [closed]

Also how do you restrict the domain to be integers in wolfram alpha?
0
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3answers
236 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
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2answers
4k 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?
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1answer
15k 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
554 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
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1answer
1k 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. $ ?
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1answer
113 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
115 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 ...
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1answer
183 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
278 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
3k 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
640 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: ...
4
votes
2answers
16k 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
3k 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
192 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
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2answers
562 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
886 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
773 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 ...