Questions on the analytic and numeric equation solving functions of Mathematica (Solve, Reduce, NSolve, FindRoot, DSolve, RSolve, etc.).

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3
votes
1answer
110 views

plotting a function on a (x,y) plane

I looked at different questions asked concerning the error message that I get but it did not help. I try to plot a function. Here is the code that I use ; ...
1
vote
0answers
79 views

Truncate an infinite continued fraction at order 2000

I want to solve an equation which contains an infinite continued fraction F(n). Then I must (obviously) truncate this continued fraction at n=2000. The problem here is tha Mathematica does not ...
0
votes
0answers
65 views

Solving system of Fredholm integral equations of the second kind

How can we generalize the code previously introduced to solve the Fredholm equation of the second kind to the case of a system of Fredholm integral equations of the second kind? $$ ...
3
votes
2answers
253 views

How to propel the integration of time a little bit further? Numerical solution can not evolve to the max time

I try to solve a nonlinear partial differential equation. I obtain a numerical solution which can not continue to the max time I set, I always receive message NDSolve::ndcf: Repeated convergence ...
1
vote
1answer
99 views

Wrong root when using numerical values

I have the following inequality: $$ \sqrt{\frac{a}{2x}}+ \frac{b}{1-\frac{a}{a+\sqrt{a(2bx + a)}}} + \frac{a}{2x\frac{a}{a+\sqrt{a(2bx + a)}}\left(1-\frac{a}{a+\sqrt{a(2bx + a)}}\right)} < f $$ on ...
3
votes
2answers
732 views

Methods for NSolve

I've been using NSolve a moderate (50-100 equations) size system of linear equations and it has been working splendidly (Solve ...
3
votes
4answers
503 views

NSolve didn't get the answer for my equations within 24 hours

I have two polynomials as function of $wa$ and $wb$ , I am going to show those polynomials. This is the expression for $GS65$: ...
1
vote
1answer
60 views

Solving a system of non-linear equations?

I want to solve the following system of equations: ...
1
vote
0answers
169 views

Help with calculating a complicated integral

Edit: The question is solved : )) Thank you for your attention ! I am sorry for mass questions, but the question bothers me a lot. So I would like to ask this question here. This problem arises when ...
0
votes
0answers
65 views

Finding double inverse Laplace transform numerically

Edit: I asked Prof. Valko, he was so nice to point out where the mistake is. The problem is solved ! Thank you for your attention ! Recall the the double Laplace transform of a function $f(x,t)$ is ...
3
votes
1answer
87 views

Dsolve and Differential Equation for botnet defence

I am currently using Mathematica to solve $\frac{\mathrm{d}x(t) }{\mathrm{d} t} = cv_{H} (1-x) + \beta x(1-x) - (\gamma_{min} - v_{D}(\gamma_{max} - \gamma_{min}))x$ with $ x(0) = 0$. In the ...
3
votes
1answer
100 views

How to solve coupled multi-variable polynomials?

The following code generates two polynomials $q_1$ and $q_2$ in complex variables p and c: ...
3
votes
1answer
84 views

Solving a list of equation which takes so much time

I try to solve a list of equation in a following way but it Mathematica solves equations after 30-40 minutes or don't solve them at all. The functions that I use are ; ...
1
vote
2answers
118 views

steady state conditions

I want to find the steady state value of variables in NDSolve but the variables have oscillation. Do you help me? ...
3
votes
4answers
78 views

Constructing a matrix of solutions using findroot

I would like to solve the following equation numerically: Sinh[y]-(y+Tanh[x])Cosh[y]-y Sech[x]^2==0 I would like to do it by creating a list of x values: ...
7
votes
1answer
226 views

Synchrotron Radiation and ListDensityPlot

I'm trying to reproduce the following plots: As described by this blog entry: Synchrotron radiation As you can see in the linked article, the task is essentially to make a ...
0
votes
1answer
45 views

Solve equations and express with specific varible

I have two equations as below: eq1: $8 \pi \gamma r-\frac{4 \pi \text{Delta$\_\mu $} r^2}{\text{v$\_$c}}=0$ eq2: $\text{Delta$\_\mu $}=\text{K$\_$b} S T$ When I try ...
1
vote
1answer
295 views

How can I use Mathematica to solve a Stefan Problem using an explicit scheme?

I would like to plot the temperature distribution for a particular case. the problem is stated in the paper, behind a paywall here, summarized as Consider a one-dimensional container of length l, ...
3
votes
1answer
112 views

Randomly generate points on a van der Waals surface

I'm looking to randomly place an atom $\mathbf{A}$ onto a van der Waals surface formed by atoms $\mathbf{B}$, such that the distance between the randomly-generated atom $\mathbf{A}$ and the nearest ...
3
votes
0answers
100 views

How to solve partial differential equation

How to solve in Mathematica this partial differential equation: $0.5\frac{\partial t(x,y)}{\partial x}+1.5\frac{\partial t(x,y)}{\partial y}+t(x,y)=y\cdot \sqrt{1+x^{3}}$ with condition $t(1,y)=y+2$? ...
1
vote
2answers
43 views

ParametricNDSolve and NDSolve inside Manipulate environment

I have a system of three coupled differential equations that can be pretty readily solved by NDSolve: ...
2
votes
4answers
241 views

solve equation with loop

I want to solve equation with different variable and list answers in a table how can Solve it in a loop (Without repeating the equation) ...
5
votes
4answers
192 views

How to find a starting value that is closer to the solution?

I am trying to solve the following system. Firstly I have a table of numerical values I will call numbers ...
0
votes
1answer
78 views

solve equations

I want to find the solution of these equations: ...
5
votes
1answer
64 views

How to solve an equation system whose equations are based on Mod[x,y]

I'm trying to find the parameters of a specific linear congruential generator (pseudo random number generator) based on a list of the first five numbers generated by it. The list is this one: ...
0
votes
0answers
102 views

Unequal behaviour of FindRoot to two similar functions

Unfortunately, I have some difficulties to plot a function. Here is my code: ...
1
vote
1answer
74 views

How to input equations for Solve

I'm trying to input: $$\log_{\sqrt 3}\frac{7-2x}{x+3}-\log_{\frac{1}{\sqrt 3}}(x+3)=\log_{\frac{1}{3}}9$$ My try: ...
0
votes
0answers
102 views

Solve Lagrange-multliplier with arrow-security prices with nonlinear (exp) utility function

at the moment I have successfully solved the Demand function for securities in the following model: t=0 current time, 2 uncertain states with same probability in period 2 indexed with i=1 and i=2. ...
4
votes
2answers
68 views

Find Instance with Set Membership Condition

Given two vectors $u=(x_1,\ldots,x_n,a_1,\ldots,a_s) \in \{-1,1\}^{n+s}$ and $v=(x_1,\ldots,x_n) \in \{-1,1\}^n$ and a bunch of fixed vectors $c_1,\ldots,c_k \in \{-1,1\}^{n+s}$ and $b_1,\ldots,b_k ...
2
votes
1answer
670 views

How to guess initial complex value for FindRoot

I have to solve a transcendental equation for a parameter, say $\beta$. Now, the $\beta$ has a range from $ik$ to $k$ where $i$ is the usual imaginary root $\sqrt{-1}$ and $k$ is a real number. ...
14
votes
1answer
1k views

What are the algorithm details of FindRoot?

The Help page of FindRoot says: "by default, FindRoot uses Newton's method (Newton-Raphson) to solve a nonlinear system". But I ...
1
vote
0answers
75 views

Coupled ODEs with boundary conditions - DSolve Error [closed]

I'm relatively new to mathematica and I can't find the error here. I suspect it has something to do with the fact that vx, vy, vz aren't blue on my mathematica - as in, they already have some assigned ...
6
votes
2answers
2k views

Error entering equation in DSolve

I entered a command incorrectly as follows: DSolve[{y'[x]=y[x]},y[x],x] I am now experiencing: ...
0
votes
1answer
355 views

Solve function doesn't work

I have the following system of equations that I need to solve: ...
0
votes
0answers
463 views

Poincare Section of an Hamiltonian

I'm in desire to plot the Poincare Section of a differential equation defined by a hamiltonian system. The hamiltonian is as follow: ...
3
votes
1answer
145 views

solving system of non-homogeneous advection equation using mathematica?

This question is followed up from this question How to solve a certain coupled first order PDE system Here I consider the non-homogeneous advection system \begin{equation} ...
6
votes
3answers
71 views

Using Select on a 2d table with a criteria that accepts 3 parameters

I have a table sets := Table[{i, j, k}, {i, 1, 10}, {j, 1, 10}, {k, 1, 10}] and I want to use a function that accepts three parameters and returns a boolean, as ...
3
votes
2answers
71 views
2
votes
1answer
113 views

Problem with implementing Regula Falsi [closed]

I checked the "Questions that may already have your answer" and didn't really find what I need. It's actually pretty basic. I want to solve an equation manually with Regula Falsi. I dont need a ...
-1
votes
1answer
100 views

Solve failing to solve system of two polynomial equations

I have two equations: $$P_a=P_a(x,y)$$ $$ P_b=1-P_a(x,y) $$ $P_a$, $P_b$, $x$ and $y$ are probabilities so their values are between 0 and 1. If I know the values of $x$ and $y$ I can calculate ...
26
votes
3answers
1k views

Does Mathematica have a built-in tool that allows one to operate on both sides of an equation?

Geogebra has a very neat CAS view that allows one to solve an equation step by step in the following fashion: $\quad \quad \quad \quad \quad \quad \quad \quad \quad $ You type an equation and ...
1
vote
0answers
79 views

Can equation solving be done in parallel?

I'm solving a set of equations that look like: ...
0
votes
0answers
99 views

System of differential equations - solving for a constant

I will reformulate my question in the hopes it will be more intelligible. First, I defined the functions: ...
1
vote
0answers
95 views

Solving a set of trigonometric equations

I've been trying to solve the following equations in order to plot Subscript[θ, 41] with respect to Subscript[θ, 2] from 0 to ...
0
votes
0answers
37 views

Using NSolve for Elliptic Equations over Fundamental Parallelogram in Complex Plane

I'm considering solving elliptic functions over a fundamental domain of the torus with half-periods $\omega_{1}=\pi/2$ and $\omega_{2} = \pi \tau /2$, where $\tau$ is the modular parameter of the ...
0
votes
0answers
74 views

How can I solve this system?

Can anyone help me? Consider, with H > 0 ...
0
votes
1answer
37 views

Solving a trigonometric equation for all $x$ using constant coefficients

I want to find the coefficients $a$, $b$, $c$, etc. that make an equation like $a+bx=x$ true for all $x$, but for trigonometric functions of $x$. For example ...