For questions concerning the popular computational software program published by Wolfram Research. (Note: you are more likely to get quicker and more accurate response if you ask the question on their user forum or on the Mathematica StackExchange site.)
2
votes
3answers
47 views
A way to identify a unique number '$a_1$' has performed operations on '$x$'
The problem I have is bit vague, so I will try to explain as best as I can.
Suppose we have a base number '$x$' and a set of unique number $'a_1', 'a_2', 'a_3', 'a_4'$ and so on
Now $a_1$ perform ...
1
vote
1answer
36 views
Help calculating variance of a random variable
This is related to this question Average end point of 1-dimensional random walk?
Given several discrete random variables such that $p(Z_i=1-2k)=p$, where $k$ is a small real number, and ...
1
vote
1answer
78 views
Solve autonomous ODE with Mathematica
I'm given a problem with the ODE
y'[x]=y[x]*Sqrt[4-2y[x]]
I've tried
DSolve[{w'[x] == w[x]*Sqrt[4 - 2*w[x]]}, w[x], x]
which gives me
{{w[x] -> -2 (-1 + Tanh[1/2 (-2 x - Sqrt[2] C[1])]^2)}} but ...
0
votes
1answer
19 views
Using Mathematica to solve equations - no answer returned?
I'm trying Mathematica and finding it can't seem to solve very basic equations. I started with something REALLY basic:
Solve[y == 2 x, x]
and it correctly returned that x = y/2.
Then I tried it ...
0
votes
1answer
44 views
Simplifying equation from an aggregate one
I have got the 4th order coefficient of $\epsilon$ from the equation (9) from the paper.
I got :
$$\phi_4+ \ddot \phi_4+\omega_2 \ddot \phi_2 - \Delta \phi_2+g_2 \phi_2^2+2 \phi_1 \phi_3+ 3g_3 ...
-1
votes
1answer
487 views
NDSolve simple matrix problem in mathematica
I have a problem with command NDSolve in mathematica. If we have simple second order differential equation, it is easy to write code in mathematica. But if we have matrix problem (for example 4 ...
5
votes
0answers
579 views
Choosing the branch of a logarithm
The problem: I am integrating complex logarithms over an angle $\phi$ over $[0,2\pi]$. It is quite complex (pun not intended) and I called Mathematica in to aid me. I am calculating an energy of a ...
3
votes
0answers
100 views
Perturbation problem
This is a mathematica exercise that I have to do, where $y(x) = x - \epsilon \sin(2y)$ and it wants me to express the solution $y$ of the equation as a power series in $ \epsilon$.
3
votes
0answers
147 views
2
votes
0answers
198 views
Calculate periodicity in 1-dimensional array with noise
I have a 1-dimensional array with some integers, which are periodically increasing. Something like this (1 period here):
...
1
vote
0answers
27 views
What are the available libraries or programs for finding extremes of a function with no symbolic definition?
In my current mathematical inquiry, I would like to gain insight on behaviour of a $d$-dimensional continuous function by locating its maximum over the hyperplane $\sum_{i=1}^d x_i = 1$ for $x_i$ ...
1
vote
0answers
259 views
$\int^{\infty}_{0}x^{r +s- 1}(1 + x)^{-s}(1 + x^2)^{-\frac{rm}{2}}dx$
I'm trying to solve the integral
$\int^{\infty}_{0}x^{r +s- 1}(1 + x)^{-s}(1 + x^2)^{-\frac{rm}{2}}dx$,
where $s$, $r$ and $m$>1 are positive integers.
My question is whether a closed form ...
1
vote
0answers
196 views
(Improved; Kindly assist )CSI Forensic Maths
In a square room with 7 m-long sides, five people have shot at random people. They all had two bullets and killed two people in the crowd. Other people in the room were not hurt. CCTV recordings show ...
1
vote
0answers
277 views
How to make iteration for Newmark method in Mathematica 8
How to make iteration method for solving differential equations by Newmark method? There are just three equations which describe the Newmark method. I need q for time step for example 0.01. Also, for ...
1
vote
0answers
163 views
Euler method on differential equation problem
I have this problem to solve.
I want to compute the inclination of a plane $\theta(t)$ at every frame of a simulation given the following rule for its angular speed of rotation $\omega(t)$
$$ ...
1
vote
0answers
378 views
Mathematica: How to convert scales to frequencies?
According to the transform $$w(u,s)=\frac{1}{\sqrt{s}}\int _{-\infty }^{\infty }x(t) \psi ^*\left(\frac{t-u}{s}\right)dt,$$ the frequency should be $f=\omega/(2\pi)=1/(2\pi s)$ (is it right?), where ...
0
votes
0answers
12 views
Lead operator problem
Define the lead operator $L^{-1}$, by $L^{-1}E_t X_t=E_t X_{t+1}$ for any variable $X$.
Then $$(1-\frac{1}{1+r}L^{-1})Z_t-\frac{r}{1+r}E_t Z_t=-\frac{1}{1+r}(E_tZ_{t+1}-Z_t)$$
I'm confused. How can ...
0
votes
0answers
31 views
Symbolic computations in field extensions with Mathematica
In Mathematica I would like to make symbolic computations in field extensions. For example, if $a$ is a root of $x^3+3x-1$, I would like to get
$$ a^4 = a-3a^2 $$
if I asked the machine to compute ...
0
votes
0answers
35 views
Problem in soution similarities
Details on the article Article
From the article equation (9) I got the forth order expansion,
$$ \ddot \phi_4+ \phi_4= a\cos 2 \tau+b \cos \tau+ c \cos (2 \tau-3)+d(\cos2 \tau-3)^2+e \cos^2 \tau+f ...
0
votes
0answers
58 views
Unit tangent, normal, and binormal vectors for a given $r(t)$
I need to find $T(t), N(t)$, and $B(t)$ for $t=1, 2, and -1$ for my Calc III class, given $r(t)=\{t,t^2,t^3\}$.
I've got Mathematica, but I've never used it before and I'm not sure how to coerce it ...
0
votes
0answers
50 views
Simulating the balls and bins problem in Mathematica (or similar)?
The 'balls and bins' problem
Distribute $n$ balls into $d$ bins in a way which minimises the difference between the highest and lowest loaded bins.
Reasoning for performing simulation
I have some ...
0
votes
0answers
107 views
A (contour?) integration (even if by using Mathematica!)
I need to be able to calculate integrals of this type where the sum over $R$ is the sum over representations of a Lie group $G$ on whom $dU$ is the Haar measure and $\chi _ R ()$ is the character of ...
0
votes
0answers
26 views
generating random density operators
A quantum (mixed or pure) state is a Hermitian, positive semi-definite operator with unit trace. I need to construct states by using available pseudo-random number generators (I personally use ...
0
votes
0answers
102 views
0
votes
0answers
106 views
How can I show that a given system of differential equations is stiff?
I was writing a program to solve a system of equations with Runge-Kutta method, but it doesn't work well and I decided to check what Mathematica can say about it. It turns out that I have a stiff ...
0
votes
0answers
178 views
Methods to solve a system of differential equations which aren't depend on a time parameter
I have a mathematical model of a Continuous stirred-tank reactor which I want to apply to a salt leaching process. After consulting with teacher and digging some literature I end up with a system of ...
0
votes
0answers
50 views
Solving the angle from one equation
I've created the following equation that represents a relation-ship among points:
x = d/(d-sin(a)*w) * cos(a)*w
I want to know the angle (a) that satisfies the ...
0
votes
0answers
109 views
How to find similar polynomials to satisfy certain boundary conditions on derivatives
Good afternoon mathematics members. I have one problem with polynomial functions.
For these functions, I need to find similar like in attachment. Derivative in start and end point and boundary ...
0
votes
0answers
90 views
How to find all permutation groups of Matrix [A] with Mathematica
Here is the Matrix A, a $9\times 9$ matrix
$$\left[\matrix{ 1& b& 0& 0& 0& c& 0& 0& a\cr
b& 2& d& 0&0& 0& 0& 0& 0\cr
0& d& ...
0
votes
0answers
45 views
Using Fit on functions that use matrix calculation
I am struggling with using Fit to fit a (linear combination of a) list of functions, that are calculated using matrices. It seems Mathematica internally uses ...
