For questions related to usage of Wolfram Alpha.

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1
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1answer
375 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
156 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
830 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
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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
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1answer
86 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
votes
2answers
58 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
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1answer
115 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
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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
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2answers
125 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
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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
97 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
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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
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2answers
349 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
429 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
189 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
126 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
328 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
599 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
427 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
221 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
856 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
128 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
103 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
2k 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
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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
135 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
266 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
115 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
77 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
132 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
835 views

Mathematica vs Wolfram Alpha integration results

When I insert the following integration command in wolframalpha: ...
1
vote
0answers
99 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
194 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
398 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
237 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
707 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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1answer
825 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
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4answers
640 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
125 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
722 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 ...
0
votes
1answer
454 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
votes
1answer
62 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
vote
2answers
672 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
574 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
1k 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 ...