# Questions tagged [wolfram-alpha]

For mathematical questions related to the usage of Wolfram Alpha.

99 questions
101 views

### $\prod_{k=2}^n (k^2 - k)$: is WolframAlpha wrong?

I tried to find the product of $k(k-1)$ from $k=2$ to $n$. The partial product values should be 12 at 3 and 144 at 4. But it's showing the wrong partial product. What went wrong? Screenshot
71 views

### Why is the solution to this sum of two sines so complex?

While working on a signal processing problem, I found I needed to solve a certain equation involving a sum of a sequence of sines. Since I wasn't really sure how to do this cleanly, I decided to ask ...
144 views

### How wolfram defines injectivity?

I was looking for a fast way of getting which function is surjective and injective. So I tried to find such command in wolfram and surprisingly it says to me that $ln(x)$ is not injective. Link to ...
2k 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 ...
319 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 ...
322 views

### On convolution and a possible bug in Mathematica/Wolfram Alpha

Let $f:\mathbb R_+\to\mathbb R_+$ be defined as $$f(x)=\frac 1{x^n}\text{u}(x)$$ where $n$ is a positive integer and $\text{u}$ is the unit step function. Define $g$ as the convolution of $f$ with ...
72 views

### Strange things on WolframAlpha: derivation, modulo and doubling result

I asked WA what is the derivative of $\frac1{\cos((x \bmod \pi/2)-\pi/4))}$ equal to for $x=0$. A very strange result came out. The exact result is $-\sqrt2 \mathsf{Mod}^{(1,0)}(0,\frac\pi2)$, ...
57 views

### Wrong Wolfram alpha result on $nth$ derivative?

I'm working with this function $$f(x)=\left(x+\sqrt{x^2-a}\right)^{-b}$$ and I would like to know the $nth$ derivative of $f(x)$. To this end, I ask Wolfram alpha about that given me the following ...
107 views

### How can I compute a fourier series with Wolfram alpha?

How can I compute the Fourier series of a function on a interval using Wolfram ? For example, the Fourier of $f(x)=x^2$ on $[0,2\pi]$ prolonged on $\mathbb R$ by $2\pi$ periodicity. For example, if I ...
179 views

### How can I restrict a variable to a given domain in Wolfram Alpha?

Ever since I began using Wolfram Alpha for quick online calculations I have had trouble specifying the domain of my variables. Note that I have already read the related MSO question "Tell Wolfram ...
116 views

### Right-to-left cycle multiplication in Wolfram alpha

Wolfram alpha carries out cycle multiplication from left-to-right. If the context dictates a right-to-left (function composition) operation, there probably is a way (short of rearranging the order of ...
56 views

### Why here is crooked line in $\log(\frac{a+1}{c+1})$ contour plot?

I plotted contour plot of this formula by Wolfram Alpha $$\log(\frac{a+1}{c+1}), 0 < a < 1000, 0 < c < 1000$$ the contour plot of the above formula In the above figure, there is a ...
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### How to solve $x$ for an equation with $x$ as an exponent and an argument of a logarithm?

I have the following equation: $$2^{-\frac{1}{x}}+1=-\log_2\left(\frac{1}{x}-1\right)$$ I can't find a way to solve it. I got it by the function $f(x)=\frac{1}{1+2^{-\frac{1}{x}}}$ when I was ...