For questions related to usage of Wolfram Alpha.

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0
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1answer
303 views

Specifying complex domain in Wolfram Alpha

Hopefully this kind of question is ok, have seen a couple of other WA-queries that hasn't been downvoted. Apologies if not. I'm trying to find the max/min of a complex function over certain domains, ...
0
votes
2answers
163 views

Wolfram Alpha unexpected answer.

http://www.wolframalpha.com/input/?i=5+%2B+%286.7a%29%2B+%28a+%5E+0.8%29 What does "imaginary part" mean?
0
votes
3answers
511 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
3answers
104 views

Derivative of $x^2-\frac{1}{x^2}$ not matching WolframAlpha result

I was calculating a very simple derivative of $$ f(x) = x^2-\frac{1}{X^2} $$ and my result is $$ f^{\prime}(x) = 2x + \frac{2}{x^3} $$ But I can't explain why WolframAlpha says the result is $2x$. ...
1
vote
2answers
131 views

How can these two be equivalent (wolfram-alpha incorrect) !?

So wolfram-alpha reads The integral of $$\int \frac{1}{\sqrt{a^2-x^2}}dx=\tan^{-1}\left(\frac{x}{\sqrt{a^2-x^2}}\right)$$ but that $$\int\frac{1}{\sqrt{a^2-x^2}}dx \;\mathrm{where}\; a=5 ...
1
vote
1answer
385 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 + ...
6
votes
1answer
159 views

Derivative of $\sec^{-1} e^{2x}$, my answer differs from wolfram alpha.

The problem: Find the derivative of $\sec^{-1} e^{2x}$ (\arcsec doesn't seem to work) My work: $u= e^{2x}$ $\mathrm{d}u = 2e^{2x}\,\mathrm{d}x$ The formula I know for the derivative of arcsec(u) ...
3
votes
0answers
889 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 ...
4
votes
2answers
6k views

Tell Wolfram Alpha that a variable is a natural number

how can I tell Wolfram Alpha that some variables are natural numbers, when I want to solve a equation? Cheers What I want to do: $\binom{n}{k}\cdot p^k \cdot (1-p)^{n-k} = \frac{1}{\sqrt{n\cdot p ...
1
vote
1answer
87 views

Inputting complicated equation into Wolfram

I am having a bear of a time getting this equation into Wolfram so I can solve it for E(r) = 1000. Everything is constant except for little r, which is the cursive r in each term. In case anyone ...
0
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2answers
62 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 ...
3
votes
1answer
2k views

Using Wolfram Alpha to solve a system of linear equations

How do I input the below system of equations in Wolfram Alpha in order to solve for the unknowns? I'm wondering if there's some kind of code that can be written in order to make wolfram alpha ...
0
votes
1answer
120 views

Solve equations in Wolfram with given variables

I am trying to use an equation as a template in Wolfram Alpha where the variables change. The equation is $-n = m - x\left\lbrack a - w\left(x - \frac{2l}{3}\right)\right\rbrack - w\left(x - ...
1
vote
0answers
63 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 ...
2
votes
1answer
64 views

Wolfram-Alpha's choice of $k$ in a complex logarithm

I'm puzzling on this complex integral: $$ \int \frac{2ie^{it}}{2e^{it} - 1}dt = \log(2e^{it} -1)$$ The numerator is the derivative of the divisor, so the primitive is the log of the divisor. When ...
2
votes
2answers
126 views

WolframAlpha seems to suggest that $log(z) = log(-z)$

Wolfram-Alpha returns this snippet at the end of the "step by step solution": I'm confused by the negation of the expression inside the logarithm. The definition of complex logarithm is: $$log(z) ...
0
votes
1answer
1k views

Matrix math syntax in wolfram alpha

I'm having trouble getting Wolfram Alpha to do my bidding with regard to matrix manipulations. I am trying to take the derivative of the following matrix expression with respect to ...
1
vote
2answers
130 views

What is this question asking me? Help appreciated!

I was wondering if anyone would be able to help me understand what this question is asking me. How would I go about working these out on Wolfram Alpha? I'm not too sure how to input them. Any help is ...
2
votes
1answer
98 views

Is WolframAlpha computing this radical correctly?

Is WolframAlpha computing this radical correctly? $$\sqrt{\frac{1}{1 + {10}^{-375}}}$$ When I double-check again, the inequality: $$\sqrt{\frac{1}{1 + {10}^{-x}}} > 1$$ leads to a ...
0
votes
1answer
2k views

Label x axis in radians WolframAlpha

I am trying to graph a trig function in WolframAlpha. I want the x axis to show radians. It will do this for a basic function, such as $y=\sin x$, but for many functions it will just label the x axis ...
1
vote
2answers
367 views

Falling/Rising factorials on WolframAlpha

Is there any notation to input falling or rising factorials on WolframAlpha?, the site has info about but i cant find nothing more.
0
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1answer
459 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
199 views

What's wrong with Wolfram Alpha (or me)? Integral involving exp(-t)

The integral in question $\int e^{-t}\cdot (1+e^{-t})^{-2}dt$ can be solved with an easy $u$-substitution. I'm getting $(1+e^{-t})^{-1}$ which I can verify is correct by derivation. I'm rusty though ...
3
votes
2answers
128 views

Wolfram double solution to $\int{x \cdot \sin^2(x) dx}$

I calculated this integral : $$\int{x \cdot \sin^2(x) dx}$$ By parts, knowing that $\int{\sin^2(x) dx} = \frac{1}{2} \cdot x - \frac{1}{4} \cdot \sin(2x) +c$. So I can consider $\sin^2(x)$ a ...
-3
votes
4answers
339 views

Why does Wolfram Alpha say that $\sqrt{1}=-1$? [duplicate]

Why does Wolfram Alpha say that $\sqrt{1}=-1$? Is this a mistake or what? Can anyone help? Thanks in advance.
2
votes
1answer
622 views

Input integral derivative in Wolfram Alpha

How to input $\frac{d}{dx}(\int_0^x \sqrt{t^2-t+1} \,dt)$ in Wolfram Alpha? If i change $dt$ by $dx$ it works, but the output is $\sqrt{t^2-t+1}$, there is no substitution for "$t$" there, if i am ...
0
votes
1answer
439 views

Input expression with summations in Wolfram Alpha

Wolfram understand this expression , but i need to do the limit when n tends to infinity of that expression . As you can see in the wolfram web itself, in the last link it fails to understand the ...
0
votes
1answer
240 views

Large system of equations using wolfram alpha.

I'm trying to use Wolfram Alpha to solve a very large system of equations- Variables A through P with a Z. It has 40 equations, so it won't let me use the regular type in the first bar. I tried using ...
2
votes
1answer
863 views

How to compute the modular multiplicative inverse on WolframAlpha?

$e = 17$ $\varphi(3233) = (61 - 1)(53 - 1) = 3120$ Compute d, the modular multiplicative inverse of e (mod φ(n)) yielding d = 2753. ...
1
vote
2answers
132 views

derivative, the way to show in a graph

http://www.wolframalpha.com/input/?i=derivative+x%5E2%2C+x%5E2 Just reminding myself some math.. Is it ok to show the derivative in such a way like was shown in the link above for $x^2$ function? A ...
1
vote
1answer
106 views

Nonlinear regression analysis of a vector

I'm trying to get a nonlinear fit of a vector in Matlab with no success. Let's assume that I have a vector called data: data = [1,30,250,55,22,76] which can be ...
2
votes
1answer
3k views

How to input this into Wolfram Alpha?

I wish to simplify a sum by doing "simplify sum_{a=0}^L f(a)" where $f(a)$ is just some arbitrary expression, but I want to only do the sum when some condition is met. Using the Iverson brackets, I ...
1
vote
1answer
56 views

Using Wolfram to convert a value chart into graph

Is it possible to use Wolfram Alpha to make something like this into a graph and have it display the proper function? In that case, how would I syntactically write it in Wolfram?
1
vote
1answer
1k views

How do I input these interval equation in to wolfram to show me the solution

How do I enter these equation into wolfram to show me the interval type equation which gives the solution as exact values.. Question 1 : $2\tan x\cos x = \tan x$ where $0\leq x< 2\pi$ Question 2: ...
0
votes
2answers
136 views

How do I enter the equation $y=\sin\frac{2\pi }{3}x$ into Wolfram Alpha? [closed]

How do I enter this equation into wolfram? Any help would be much appreciated. I'm not sure how to do the brackets. $$y=\sin\frac{2\pi }{3}x$$
2
votes
3answers
271 views

arithmetic operations on alephs in WolframAlpha

Can someone please enlighten me if or how both of these facts can be true? I entered $\aleph_0-\aleph_0$ into WolframAlpha, which gave the result as undefined. But it also plotted the result on a ...
1
vote
1answer
116 views

Am I right or is Wolfram right?

Let ${a_n}$ be a sequence whose corresponding power series $A(x)=\sum_{i\geq 0}a_ix^i$ satisfies $$A(x)=\frac{6-x+5x^2}{1-3x^2-2x^3}$$ Determine a recurrence relation that ${a_n}$ satisfies. I ...
4
votes
1answer
78 views

Polar coordinations - problem with r and $\theta$

let's take a look on Archimedean spiral. the polar equation is $r = \theta$. click here to look. but $\tan (\theta) = y/x$ and $r = \sqrt{x^2+y^2}$, so $r = \theta \rightarrow \tan(\sqrt{x^2+y^2}) ...
0
votes
2answers
138 views

Series expansion with remaining $log n$

I'm studying the asymptotic behavior $(n \rightarrow \infty)$ of the following formula, where $k$ is a given constant. $$ \frac{1}{n^{k(k+1)/(2n)}(2kn−k(1+k) \ln n)^2}$$ I'm trying to do a series ...
0
votes
1answer
894 views

Mathematica vs Wolfram Alpha integration results

When I insert the following integration command in wolframalpha: ...
1
vote
0answers
111 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 = ...
5
votes
1answer
199 views

Why doesn't $ \lim_{(x,y)\rightarrow(0,0)} xy\sin(\frac{1}{xy}) $ exist?

I've tried to get the following limit: $$ \lim_{(x,y)\rightarrow(0,0)} xy\sin\left(\frac{1}{xy}\right) $$ wolfram claims it doesn't exist. How to show that? Why can't I take $z=xy$ and receive a ...
1
vote
1answer
417 views

Numerical values of the Jacobi elliptic function sn: Wolfram Alpha vs. Maple vs. C++?

I have a problem to check the validity of an algorithm I've implemented in C++ to compute the Jacobi elliptic function $\mathrm{sn}(u, k)$ (inspired and improved from Numerical Recipes 3rd edition). I ...
0
votes
1answer
242 views

Is Wolfram Alpha correct?

Given the attempted derivative at http://www.wolframalpha.com/input/?i=d%28a%28x%29+choose+b%28x%29%29%2Fdx, I believe the result from Wolfram Alpha is off by a factor of 2 or, at least I get a result ...
0
votes
2answers
723 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
votes
1answer
904 views

What does a dot after a number mean?

So I'm making some calculations for numerical analysis and the output I get in Wolfram or Mathematica for input like: ...
13
votes
4answers
646 views

The last few digits of $0^0$ are $\ldots0000000001$ (according to WolframAlpha).

Can anybody explain how this comes about?
2
votes
4answers
3k 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 ?
1
vote
3answers
126 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
749 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 ...