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

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How to select one solution of a system? [duplicate]

The system, Solve[{F[x,y]==0,G[x,y]==0},{x,y}] has to solutions {{x->x0,y->y0}} How can I choose, for example, ...
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1answer
165 views

Why timing of FindRoot is almost the same even if the function is speedup significantly

This question is almost the same issue as this one. However, it seems that it didn't draw enough attention. Now I encountered the same problem. I previously make this post, I will copy the code here. ...
0
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1answer
75 views

How to plot a solution set? [duplicate]

I have two functions, let's call them $F1$ and $F2$. Both take the same three arguments: $x1, x2$ and $\epsilon$. With every $\epsilon^* \in [0,1]$, there should be either zero or one unique point ...
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2answers
106 views

Solve implicit system of equations

Hello everybody I try to solve this system of functions and try to plot it: x == 0.5(1.+Tanh[0.5*(x*y^2-eps1)/t] y == Tanh[(x^2*y+eps2)/t] with eps1 = 0. and ...
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2answers
72 views

How to Count the number of roots in the Domain from an equation

How do i Count[] the number of roots in the Domain and printout the intervals in x containing these roots. Given the function ...
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0answers
4 views

Finding multiples of three given a few simple rules [migrated]

We were given this problem the other day and it seems a little over my head, so I thought I'd share it here for any possible advice or assistance :). The problem is as follows: Initially, x = 1. For ...
3
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3answers
176 views

Cantor Pairing Function

I'm inspecting the Cantor pairing function, that we can find on this link here. But the strange thing is that Mathematica is outputting a wrong result to me. The code below shows the strange ...
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2answers
340 views

Solving pure functions

I've been trying to use Solve with pure functions to receive function efinition and then use it with Map , to obtain results from mapping function to some data. Here is example ...
2
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1answer
47 views

best way for finding approximate root of monotonic sawtooth like function

First I will generate such kind of monotonic sawtooth like function called func ...
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0answers
57 views

Reduce function with simultaneous equations and inequalities

I have some simultaneous equations that I want to solve, preferably analytically, yet I am unsure if the Reduce function is the correct route as it doesn't seem to ...
2
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1answer
101 views

Maximize a variable in NSolve Function

I want to solve a set of trigometric coupled equations with the NSolve funcion while at the same time trying to maximize a variable which has to be real and between ...
0
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1answer
63 views

Solve equation in a interval

I have a particle bouncing in a rigid box, my code is this: ...
0
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1answer
36 views

How can I set a solution of NSolve into the variable [duplicate]

I am trying to solve an equation such as: NSolve[Integrate[G[x], {x, -∞, ∞}] == 1 && B > 0, B] when ...
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1answer
89 views

Solve the interpolating function

I would have asked how to obtain the x given the y in an interpolating function, and I found the answer from here. But another question raised. I was dealing with measurement of the spectral ...
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2answers
41 views

how do I find the unknown coefficients of coupled equations

How do I find the unknown constants $x, y, z$ interms of a and b, using Mathematica. \begin{equation} \begin{split} 1&=-x+y+z \\ ...
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1answer
39 views

Expanding in terms of a function in Solve

I am almost sure Mathematica has a way to do what I am looking for. I am trying to fit a quadratic T(x) = ax^2 + bx + c to three values of the function analytically. I proceed as follows: ...
4
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3answers
211 views

Solving equation

How can I solve this equation: ((a^2 - 1)*((a^2 - 1)*ArcTanh[a] - a))/(2*Sqrt[2*(a^2 - 1)^4]) == C*x I am looking a solution for $a$ in function of $x$. I tried ...
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0answers
42 views

Impose conditions on differential equations

This is my first post in Mathematica Stack Exchange, so thanks for your help and sorry for any rookie mistakes. I am solving the Einstein equations for two vectorial pertubations h_Alpha and v_Alpha ...
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1answer
39 views

“MemoryAllocationFailure” in DSolve

Mathematica 10.4, Windows 10, 6 GB RAM, 64 bits When I trying to solve DSolve[{v'[t] == 100 - 0.15 v[t]^2, v[0] == 30}, v[t], t] I get ...
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0answers
39 views

Using previous outputs and equations for 3d plots

I am extremely new to Mathematica, and am trying to obtain some plots for my research work. I need to find the roots of a polynomial, and using the roots individually, I need to obtain another ...
0
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0answers
92 views

Impose a boundary condition to a function

Background I am trying to impose a boundary condition on a function of two variables $u(x_1,x_2)$. The boundary condition is: $u(x_1,0)=A\cos(\omega x_1)$. The same function in mathematica ...
2
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1answer
119 views

Differential Equation with Numerically Integrated Boundary Conditions

I have a second order differential equation that I'd like to solve numerically, and then integrate its solution twice to get the parametric equations of a curve. The ODE is: $2 ...
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0answers
42 views

Hash in Eigenvalue calculation [duplicate]

When I tried to find the eigenvalue of a 5x5 matrix, I get the following ...
0
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0answers
47 views

Solve huge system of inequalities

I need to solve the huge system of algebraic linear inequalities (up to milions). But the built-in methods like Solve, Reduce, FindInstance... seems to be very slow. I have problem to solve "only" 100 ...
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4answers
348 views

Equation for the line of intersection between two planes

I have two equations: 2x + y + z = 1 3x - 2y - z = 5 And I have calculated the answers on paper, which gave me $x = 1 + t$, $y = -1 + 5t$ and $z = -7t$. So my ...
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0answers
34 views

Solvability of a system of equations and inequalities

I want to know if a given system of equalities and inequalities is solvable or not. I do not need the solution, rather just about its solvability. I tried a few variations, but I believe that it can ...
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2answers
96 views

Solving recursion relation from power series

I am interested in solving differential equations in the form of power series. Let's say we have following equation: $$f^{\prime \prime} (\rho) + \left( \frac{2 e^{-k \rho}}{\rho} - \varepsilon ...
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1answer
74 views

norm squared of imaginary function with unknown constants

Is it possible to evaluate the norm squared and expand a given function similar to this, $$ ...
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2answers
62 views

Finding roots of a function that includes Bessel functions [duplicate]

I'm fairly new to Mathematica so forgive any stupid mistakes. Here's my function: ...
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1answer
62 views

Differential equation [closed]

How does one solve this differential equation? $$y' = \frac{x^3 + 2x^2 y - y^3}{x^3 + x^2 y}$$
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1answer
41 views

Select positive solution based on value of parameter

I want to select positive solutions to Solve[], but as the sign of the solutions depend on the value of some parameters/other variable, I am not sure how to do ...
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2answers
79 views

Solutions to Non-linear equation system

I have been trying to solve the following system of equations: ...
1
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1answer
56 views

System of polynomial equations with Solve does not converge

The Exp-method [1] is an analytical solution method for differential equations. Essentially, the method boils down to the solution of a system of nonlinear polynomial algebraic equations. In [1] (and ...
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0answers
34 views

Why differential equation reduces? [duplicate]

I am trying to ND-Solve the following equation: eqns = {x''[t] == -x[t], x'[0] == 0, x[0] == 4} The problem, is when I enter it, Mathematica reduces it to ...
1
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1answer
58 views

Precision in calculation [duplicate]

I am writing some code to demonstrate the effect of the number of significant figures a coefficient has on the solution of a nonlinear equation. I define the coefficient as follows: ...
0
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1answer
78 views

NDSolve for a system of nonlinear coupled pde

I try to solve a system($n$) of coupled nonlinear 1-d PDE's which is basically coupled sine-Gordon equations (through 2nd spatial derivative) in time and space. I am interested in the dynamics when I ...
0
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1answer
95 views

Find partial solution for underdetermined system of Boolean equations (Minesweeper)

In this article about creating a Minesweeper solver, the author talks about using matrices to solve given portions of a Minesweeper board. While reading that, I thought of a different way to limit the ...
5
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1answer
398 views

How to solve this Integral equation

D[x[t] - x[t - 1]/(2 E), {t, 3}] + Integrate[E^(-δ)*x[t - δ]/5^t, {δ, 2, 2.5}] == 0 I found solve this problem is hard with Mathematica. I also find a article ...
2
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0answers
53 views

Estimating processing time for commands

I am trying to evaluate some equations by using Taylor series of expansion (Series[], ExpandAll[], and Normal[] command), and using n equation and n unknown (Solve). Following is not full command (if ...
0
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1answer
84 views

Solve non-linear system of 16 equations [closed]

I need a solution to a non-linear system of 16 equations, I am trying the following command and nothing is happening: ...
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1answer
66 views

How can I solve a certain statics problem [closed]

Does someone have any idea how to solve it or from where to start?
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1answer
47 views

Symbolic Maximization: does not work with symbolic power?

Simple question from a beginner: I seem to be unable to do maximization if the variable has a power specified symbolically instead of numerically? ...
2
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1answer
101 views

How to approximate the solution of a system of quartic equations

In an attempt to evaluate the point at which the cycle 2 becomes unstable for the given map: \begin{equation} x_{n+1}=μ-x_n^4=f(x_n), \quad μ \in \mathbb{R} \end{equation} I have so far managed to ...
2
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1answer
47 views

Passing a list to a nested vector function

In order to apply a newton-rhapson algorithm to solve a set of nonlinear vector equations such as these, f[x_, y_] = {x^2 - 3*y + 6, (y + 1)^2 - x - 33} I need ...
3
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3answers
178 views

Determine integer results using Solve

I'm trying to solve a Pythagorean pairs for m and n (for m and n < 100) which give integer p values in the following equation: Sqrt[m^2 + n^2] == p I may ...