For questions related to usage of Wolfram Alpha.

learn more… | top users | synonyms (1)

0
votes
1answer
25 views

Wolfram Alpha Step By Step For Systems of differential equation

Does anyone know if wolfram alpha has step by step solutions for systems of differential equations? When I input them, it comes up with an answer but it does not give me the step by step solution. I ...
6
votes
4answers
142 views

How many values does $\sqrt{\sqrt{i}}$ have?

Wolfram says, there are only two roots, but $\sqrt{i}$ already gives two roots. So if we express them in Cartesian form we can take square roots of them separately and end up with four roots. ...
1
vote
2answers
21 views

Integral of $-4\sin(2t - (pi/2)) $ weird behavior on wolfram alpha

I'm confused by what Wolfram Alpha is doing with my function: $$-4\sin{(2t - (\pi/2))}$$ on why the it gets replaced by $$4\cos{(2t)}$$. Is it equal? Link: See behavior here
3
votes
1answer
56 views

Repeating decimal notation of 1/53 on WolframAlpha vs notation on Wikipedia

WolframAlpha shows for 1/53 $0.0\overline{1886792452830}$ as the repeating decimal. Why is it not $0.\overline{0188679245283}$ instead? For example, Wikipedia shows for 1/81 ...
0
votes
0answers
19 views

Relations between hypergeometric functions

I am trying to find a relation between hypergeometrics $${}_2F_1(a,b,c;z)\,\,\text{and}\,\,{}_2F_1(a+1,b+1,c+1;z)$$ I can see that $$\frac{\partial}{\partial z}{}_2F_1(a,b,c;z) = ...
0
votes
0answers
9 views

Inserting “holes” on a graph.

I am trying to plot the set $A = \big\{(x,y) \in \mathbb{R}^{2} \mid x^{2} + y^{2} < 2 \big\} - \big\{(0,\frac{1}{n}) \mid n=1,2,3 \dots \big\}$. I have tried different combinations of set ...
1
vote
0answers
47 views

Maple and WolframAlpha return different results

I solved the integral of u/(1-u) by hand and found as result -ln(1-u) - u + constant. Now, when I evaluate this integral with WolframAlpha, I get the same result. But when I evaluate it with Maple, it ...
1
vote
0answers
30 views

Application of Initial Value Theorem

Let $$F(s):=\frac{s}{2s-i}$$ be the Laplace transform of some $f(t)$. I have been asked to compute $f(0^+)$ assuming that this quantity, intended as limit, exists. I thought I could apply the IVT ...
0
votes
2answers
45 views

Calculating limits with Wolfram|Alpha

in a random graph setting with $n$ vertices and edge-probability $p$ I want to show that $\binom n4p^6\to 0$ as $pn^{2/3}\to 0$. To check this is even true, I submitted this Wolfram|Alpha query. Now ...
0
votes
0answers
65 views

Solid has same volume when axis of rotation increases?

I'm working on calculating the volumes of different solids using integration. The problem I'm working on says to find the volume of two solids, one revolved around the line $x = 4$ and the other ...
0
votes
2answers
38 views

About a solution in Wolfram Alpha

I'm intrigued by this finding on the extraordinary portal WolphramAlpha. What is the reason why the solution has not been simplified, eliminating the factor $\frac{\sqrt x \sqrt{x+2}}{\sqrt ...
1
vote
1answer
26 views

CAS based math program that can evaluate two sided limits? Ex:$\lim _{x\to 0}\left(\frac{1}{x}\right)=DNE$

I am new to Calculus and would like a CAS program to check my work without any hassles. I tried evaluating $\lim _{x\to 0}\left(\frac{1}{x}\right)$, a limit where the two sided limit DOES NOT EXIST in ...
7
votes
2answers
587 views

A ''strange'' integral from WolframAlpha

I want integrate: $$ \int \frac{1}{\sqrt{|x|}} \, dx $$ so I divide for two cases $$ x>0 \Rightarrow \int \frac{1}{\sqrt{x}} \, dx= 2\sqrt{x}+c $$ $$ x<0 \Rightarrow \int \frac{1}{\sqrt{-x}} \, ...
0
votes
0answers
11 views

Plotting standard deviation function using WolframAlpha

I'm trying to plot a standard deviation function using WolframAlpha's function plotter and my function looks like this: $SD(Y) = \sqrt{\sum_{i=2}^{k}\frac{k(i-1)}{ (k-(i-1))^2 }}$ where k goes from 1 ...
2
votes
1answer
49 views

Why is $\ln(\sqrt{|2x-5|}) + \frac{1}{2} \ln(|2x+3|) \neq \ln(\sqrt{|2x-5|}) + \ln(\sqrt{|2x+3|})$ in Wolfram Alpha?

According to Wolfram Alpha, $$\frac{1}{2} \ln(|2x+3|) = \ln(\sqrt{|2x+3|})$$ is always true, which makes sense given what I know of log rules. However, if I add the expression $\ln(\sqrt{|2x-5|})$ ...
3
votes
1answer
113 views

How does wolfram alpha compute this integral?

Wolfram alpha can find that $\int_1^\infty\frac{x^8-8x^7+24x^6-32x^5+19x^4-12x^3+17x^2-10x+2}{x^{12}-12x^{11}+56x^{10}-120x^9+82x^8+112x^7-182x^6-92x^5+381x^4-356x^3+170x^2-44x+5}dx=\frac{\pi}{2}$ ...
2
votes
2answers
70 views

Error on Matlab and Wolfram Alpha?

I solved the differential equation $\frac{\mathrm{d} y}{\mathrm{d} x}= \frac{y^2-1}{2y}$, in the following way: $\frac{\mathrm{d} y}{\mathrm{d} x}= \frac{y^2-1}{2y} <=>$ $\int ...
1
vote
1answer
68 views

How to calculate $\lim _{( x,y) \to (0,0) }\frac {x^2y^{3} }{\sin ( x^{8}+y^{4}) }$?

How to calculate $$\lim _{( x,y) \rightarrow (0,0) }\dfrac {x^2y^{3} }{\sin ( x^{8}+y^{4}) }$$ Wolfram Alpha says it is equal to $0$, but if calculate by trying $y=x$ then I get the limit $\lim ...
1
vote
1answer
58 views

is ${x^{2/3}}$ the same as ${\sqrt[3]{(x^2)}}$ or ${(\sqrt[3]x)^2}$? domain?

is ${x^{2/3}}$ the same as ${\sqrt[3]{x^2}}$ and ${(\sqrt[3]x)^2}$? and what is domain of $x$? Wolfram Alpha shows different results for ${x^{2/3}}$ and ${\sqrt[3]{x^2}}$ representations. Is domain ...
-1
votes
1answer
70 views

How to use Wolframalpha to verify the solution to a DE? [closed]

I would like to find the correct syntax for Wolframalpha so that it will test my solution to a DE. e.g. if I find that $y_p = -t^2 + \frac{3}{2}t - \frac{11}{8}$ and would like to see what that yields ...
1
vote
2answers
93 views

Floating point modulus precision (high multiple)

While looking at implementing floating point modulus in double-precision on an x86 CPU, I found the FPREM instruction and proceeded to test the practical precision in some cases, one being ...
0
votes
0answers
23 views

Compare two MathML equations, expression etc

We have to develop a system where students can enter their answers for problem and system must check it with correct answer. Could you suggest any resources to solve this problem. It might be any ...
1
vote
1answer
21 views

What doesn 2nd column depict in this table for perfect number description?

I am reading about perfect number at below link. http://mathworld.wolfram.com/PerfectNumber.html I am not able to understand what does the 2nd column (pn) depict? ...
0
votes
1answer
138 views

Can I get multivariable taylor series expansion on wolfram alpha or matlab?

I need something like this : say $a, x, y$ and $t$ are three non-negative real numbers. Now define the complex number, $z = -y + i(a+x-t)$ and consider the function $f(x,y) = z\text{ }tanh (\pi z) log ...
0
votes
1answer
42 views

How to find the number of solutions to an equation in wolfram alpha

Given the equation: $$sin(x)=\frac{x}{218}$$How do I use Wolfram Alpha to find the number of positive solutions?
1
vote
0answers
92 views

A WolframAlpha error?

Consider the equation: $$ \dfrac{1}{\sqrt[3]{(x+3)^2}}-\dfrac{1}{\sqrt[3]{x^2}}=0 $$ that has the solution $x=\dfrac{-3}{2}$ as can be easely verified. But WolframAlpha gives no solutions (here). ...
6
votes
0answers
60 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 ...
1
vote
2answers
28 views

$\int_{c}^{c+2L} cos(\frac{2\pi nx}{L})$ Wolfram Alpha gives me this result but when doing I dont get it

$\int_{c}^{c+2L} cos(\frac{2\pi nx}{L}) = \frac{L sin(2\pi n) cos(\frac{2 \pi n(c+L)}{L})}{\pi n}$ dx with $n = 0,1,2,...$ I put this integral in Wolfram Alpha and gives me this result, but when I ...
0
votes
1answer
28 views

Solving system of equations

I'm trying to solve for $x$ and $y$ in the following system of of equations: $$((x-m)^2+(y-j)^2)(x-m)^2=((x-k)^2+(y-l)^2)(x-k)^2$$ $$((x-m)^2+(y-j)^2)(y-j)^2=((x-k)^2+(y-l)^2)(y-l)^2$$ I've tried ...
1
vote
2answers
99 views

Is there a reason to omit $[0]$ from the solution of the inequality $x^4 \ge x^2$?

This is the inequality I plugged in: $$x^4 \ge x^2$$ Wolfram Alpha gives me the correct number line, but the interval notation it gives me is missing $\{0\}$. (It gives me $(-∞, -1]$ and $[1, ∞)$, ...
2
votes
2answers
107 views

Indefinite integral that Wolfram Alpha can't solve

Does anybody know the indefinite integral problems that Wolfram Alpha can not solve but human can solve by using elementary functions? (The meaning of "solve" here is to represent primitive function ...
0
votes
2answers
25 views

Augmented matrix gives no solutions when augmented with variables, but will give solutions when augmented with some numbers

I have a homework problem that boils down to this: x1 = 1a + 1b x2 = 1b + 1c x3 = 1c + 1d x4 = 1d + 1e x5 = 1e + 1f x6 = 1f + 1a I write the matrix to solve for x. I row-reduce the matrix. ...
4
votes
1answer
134 views

Calculating a sum which includes binomial coeffeicients

Some formula for calculating the probablity that the difference between the number $6$ and the average of accidentally selected $100$ points among $10000$ points which are distributed in the interval ...
1
vote
2answers
77 views

Wolfram Alpha “x = derivative x”

Asking Wolfram Alpha $x = \text{derivative } x$, I was expecting $e^x$, being that the derivative of $e^x$ is $e^x$, Wolfram Alpha however yields $x = 1$. Is this stating that the derivative of a ...
2
votes
3answers
113 views

Did Wolfram|Alpha mess up $\int 1 - \frac{1}{1-e^{-x}} \mathrm{d}x$ or did I?

I want to calculate $$\int 1 - \frac{1}{1-e^{-x}} \mathrm{d}x$$ Provided that $x>0$. Substituting $u=1-e^{-x}$, we get: $$\int \frac{1 - \frac{1}{u}}{1-u} \mathrm{d}u = -\int \frac{1 - ...
-1
votes
1answer
58 views

Code Wolfram Mathematica [closed]

Sorry but I do not know English very well. The question is very simple, I hope someone knows the code that makes my case. In fact, writing: ...
2
votes
2answers
158 views

How does WolframAlpha solve quintic equations (5th degree polynomials)?

There exists no general formula for quintic equations. Then how does WolframAlpha solve quintic or higher degree polynomial. Is there a sure way to get values of roots of quintic or higher degree ...
3
votes
1answer
40 views

Simplify multinomial trig expansion to fewer linear terms like Wolfram?

I'm mystified as to how Wolfram Alpha's TrigReduce[expr] does its magic, particularly on sums of long products that look like $$A \cos^a(B_1 x) \sin^b(B_2 x) \cos^c (B_3 x) \sin^d (B_4 x) \dots$$ I ...
0
votes
1answer
116 views

Why can't Wolfram calculate the Laplace transform of $\sinh(t)\sin(t)$ correctly?

Question Show that the Laplace transform of $\sinh(t)\sin(t) = \frac{2s}{s^4+4}$. Wolfram can't calculate this as is, so I tried to simplify it a bit. I defined $\sinh(t)$ as $e^t-e^{-t}$ and split ...
3
votes
2answers
107 views

Plot of $y=x+0\sqrt{-x}$ (and WolframAlpha vs Desmos)

To plot the graph of $y=x+0\sqrt{-x}$ : Do we have to first find out the domain of $y$ which is $y \in ( -\infty,0 ]$ ? $\color{blue}{\text{[Case 1]}}$ (that's what I do) Or do we solve the ...
2
votes
2answers
126 views

Is Wolfram-Alpha giving me a wrong result?

I have to calculate: $$\nabla^2 \frac{e^{ikr}}{r}$$ which I know to be $\displaystyle -k^2 \frac{e^{ikr}}{r} $ (from a lecture). Doing it by hand: $$ \nabla^2 f(r) = \frac{1}{r^2} ...
1
vote
4answers
153 views

Is Wolfram Alpha calculating this incorrectly?

I entered in "does $2ln(x)$ equal $ln(x^2)$" into Wolfram and it came out false. Purplemath.com says that $log_b(m^n) = n · log_b(m)$. Which is correct? And why is there a difference?
3
votes
2answers
616 views

The sum of digits of $3(3x+3)$ is always $9$ for any $x$ between $1$ and $9$

Given the following 'joke' I stumbled across today It's easy enough to figure out that the answer is always 9. Asshole. However when I tried to 'prove' this for ...
0
votes
2answers
112 views

How to do multiplication (capital pi) in WolframAlpha?

How do i ask this in WolframAlpha: $$\prod_{i=0}^{i=10} \sin{(i)}$$ I used $\text{product}(...)$ and $\text{multiply}(...)$ or even $\text{multiplication}(...)$ but they don't seem to work. I am ...
0
votes
1answer
47 views

What function does Wolfram Alpha plot instead of the factorial?

Look to the second graph where Wolfram Alpha gives a continuous factorial function: What is the second graph? It is not the gamma function, since that has $\Gamma(-1)=0!=1$.
0
votes
3answers
131 views

WolframAlpha wrong(?) graph

I had a question to plot a graph of $\space \space\LARGE y=x^{x^{x^{x^{...}}}}$ Which (according to me) is equivalent to $\large y=x^y \Rightarrow y^{\frac{1}{y}}=x$ So i plotted them in ...
14
votes
7answers
2k views

Conflicting limit answers using calculator and wolfram alpha

I want to evaluate $\lim\limits_{x\to0} \dfrac{\tan(x) - \sin(x)}{(\sin(x))^3}$, Calculator says it's 0 when substituted with 0.0000000001. Wolfram Alpha says it's 1/2. The Problem Set says the ...
3
votes
2answers
152 views

Solving $\frac{dx}{dt} = A \frac{ (1-x)}{(t-t^2)} - \frac{(B*x -C*x^2)}{(t-t^2 )*(t-x)}$ (using wolfram/mathematica)

I would like to solve the following non-linear ordinary differential equation: $$\frac{dx}{dt} = A \frac{ (1-x)}{(t-t^2)} - \frac{(B*x -C*x^2)}{(t-t^2 )*(t-x)}$$ -I need an analytic solution. -I ...
1
vote
2answers
53 views

Wolfram alpha giving wrong result on recurrence?

I have the recurrence$$a_{n+2}-a_n=1$$ The answer I got was $a_n=A+B(-1)^n+\frac n 2$, while WolframAlpha is giving me $a_n=A+B(-1)^n+\frac n 2- \frac 1 4$. Although when I plug them in the ...
1
vote
3answers
434 views

Why does Wolfram Alpha say that $n/0$ is complex infinity?

I typed a number divided by 0 on Wolfram Alpha and thought that it would say "undefined". However, when I pressed enter it told me that the answer is complex infinity. I have always been taught ...