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

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1
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1answer
298 views

Why my differential equations become True?

I've been trying to solve a system of nonlinear differential equation, but the conditions are a bit weird. Two of the differentials equate to the same equation, but have different boundary ...
0
votes
2answers
65 views

NSolve gives {{ x -> #}}, How do I make x = #; I need to use the x value again later

I want to use: demand = {1.92, 2.07, 2.37, 2.72, 2.87}*10^6; NSolve[SetV == demand[[1]]/(Cpf (1 - χ)), χ] I want to make a vector of solutions ...
3
votes
1answer
194 views

Solving a large system of nonlinear equations

I have a system of 80 nonlinear equations with 64 variables to solve in Mathematica but it takes a lot of time (about two hours) and then it return "no more memory available" knowing that I have 8GB ...
7
votes
2answers
707 views

Getting an InterpolatingFunction from a ContourPlot

I have a function, say minimizeme[Ω_][β_][ϵ_] = ϵ^2 Ω - Log[2 (Cosh[2 β] + Cosh[2 β ϵ])]/(2 β); I want to find its critical points in $\epsilon$ for a given ...
2
votes
0answers
121 views

What are the steps using boolean algebra for transforming one equation into another?

I have a special case where I have two equations, which I have solved in a better and quicker way, but I need to solve with Boolean algebra. Using the laws of Boolean algebra, I have to prove that ...
2
votes
0answers
126 views

Volterra integral equation

I have to find an approximate numerical solution for the equation $$ F(x) - \lambda \int\limits_1^{x} \text{d}s \;s^2 F(s) Z(x-s) = G(x) $$ $$Z(s) = (\psi''(1-2\ h\ i\ s)- 0.5 \psi''(1-2\ h\ i\ s))$$ ...
1
vote
1answer
90 views

How To Replace $\rightarrow$ by $==$ in Mathematica's Output when using Solve

I want to create equations out of the output (solutions) produced by Mathematica when using the Solve functions. For argument's sake, consider the following. ...
0
votes
1answer
230 views

Minimize: How to work with specific numeric types

This is a question about the use of symbols in Minimize and how to persuade Mathematica to treat them in a specific way (as integers or rationals) that I have not ...
2
votes
1answer
80 views

Multiple dynamic equations for plotting?

Say I have a bunch of equations between variables e.g. h=bcd, i=hce, j=ihbd, ...
1
vote
1answer
76 views

Non-linear system of equations with a parameter

I want to solve k*x-(x-y)*y^2==0 and y+(x-y)*y^2-(1-x-y)==0 for -10 < k <10 How ...
4
votes
0answers
226 views

What is the algorithm behind Mathematicas Reduce in this equation?

Mathematica can use Reduce to arrive at an answer in this equation ...
1
vote
3answers
111 views

Applying Reduce[] to a table [duplicate]

I have a table for example: t = Table[k,{k,5}] which returns {1,2,3,4,5} and for every element in this table I want to check when it is $\leq 1 + a$. I ...
3
votes
1answer
100 views

Solving simultaneous systems of linear equations

I have several systems of linear equations in matrix form, and I would like to find the $\vec{x}$ that simultaneously solves them: $$A_1\vec{x} = b_1$$ $$\vdots$$ $$A_n\vec{x} = b_n$$ Is there a ...
25
votes
4answers
5k views

Find eigen energies of time-independent Schrödinger equation

I'm trying to get the eigenvalues of a one dimensional time-independent Schrödinger equation, $-\frac{h^2}{2m_0}\frac{d^2\psi}{dx^2}+U(x)~\psi=Ei~\psi$ where U(x) is some potential and Ei is the ...
2
votes
0answers
74 views

How does Mathematica resolve symbolic systems of inequalities?

Before getting into my (probably annoying) question, let me provide some context: I recently started using Mathematica to automatically perform stability analyses that I previously did by hand. A ...
2
votes
2answers
151 views

cycloid parametric [closed]

How do I enter 3 parametric equations for cycloids corresponding to circles with radii 1, 2, and 4. I have tried ...
2
votes
1answer
140 views

Catastrophic loss of precision

while I am trying to solve the double integral in the range of 0 to Infinity (for both the integral) it give me the error Catastrophic loss of precision in the global error estimate due to ...
0
votes
1answer
57 views

How to find the Nth zero of a function

It's an almost same question with "a multiple roots finding" but, the order of roots is important in my case. Basically, I'm trying to find Nth crossing point of the following graph: ...
1
vote
0answers
37 views

Resolve not accepting equations involving factorial

If I take , Resolve[ForAll[x,x!>=0],Integers] True But if I make slight modification, ...
2
votes
2answers
155 views

How to Map each cell in a matrix to another and solve the system?

tab1 = {{a1, a1 + a2}, {b1, b2*b2}} tab2 = {{2, 5}, {5, 2}} I want to map like this ...
1
vote
3answers
2k views

Tricks for solving (lots of) coupled nonlinear equations numerically?

I have a system of 6 non-linear (quadratic) coupled equations with 6 complex unknowns \begin{align*} |x_1|^2 + |x_2|^2 + |x_3|^2 &= a\\ x_1 x_4^* + x_3 x_5^* &= b + c i\\ x_1 ...
0
votes
2answers
91 views

Finding an idiomatic way to express a system of linear equations

I have an $n$ x $n$ matrix $T$, where $t_{ij}$ is the element at the $i\,$th row and $j\,$th column, and unknowns $x_i$, $1\leq i \leq n$, where $$x_{n} = 1$$ $$x_{n-1} = 0$$ $$x_i = \sum_{1\leq j ...
0
votes
1answer
77 views

Plotting and Analysing derivatives of solution of differential equation [closed]

Using NDSolve I found the solution for the differential equation that governs the dynamics of a simple pendulum. How do I plot the derivatives of the solution? Also, I would like to find the ...
0
votes
1answer
262 views

Using Solve but getting no output

I am trying to solve a model using a constant-elasticity-of-substitution production function, but when I try to solve the first order conditions, I just keep getting back what I typed. ...
1
vote
1answer
58 views

Missing solutions for complex equation system

I am currently working on a game-theoretic paper and trying to match two complex best response functions. The equation system includes two decision variables x and ...
0
votes
2answers
65 views

Trouble representing an equation

I'm having trouble representing the following as an equation ...
1
vote
1answer
119 views

Why is ((v k)^-n (k v^n - v k^n))/(n - 1) == b so hard for Mathematica to solve (for v)?

I've tried using both Solve and Reduce. For something that takes maybe 3 minutes to solve with paper and pencil, I'm very ...
5
votes
3answers
293 views

Equation is solved quickly using Solve but takes too long using NSolve

I have the following simple command to solve for h in an equation: Solve[(1 - 2.25577*^-5*h)^5.25588 == 0.9644952131579817, h] ...
1
vote
1answer
79 views

Plotting the results of NSolve as Horizontal Lines

Suppose I use NSolve to find the Real approximations to the intersections of two separate functions over some specified range: ...
6
votes
4answers
481 views

How to find an approximate solution in a region when Solve or NSolve does not work?

Consider the relation x/Tan[Pi x] == y/Tan[Pi y] Solve or NSolve can't give a solution ...
0
votes
0answers
96 views

simulate a 32-bit signed integer overflow in a recurrence function

Considering the following recurring equation: which is this factorial function: I want to find the value of x where f(x) = 0. Actually, the solution is impossible with Mathematica, and it's ...
1
vote
1answer
92 views

solve recursive factorial function [closed]

Is there a way to solve this recursive factorial function? a[n + 1] = (n+1)*a[n], a[10]=10 I am looking for the value of a[n] ...
0
votes
1answer
71 views

How large can be the dimension of a complex matrix which Mathematica can handle to find its eigenalues?

I have been working with 12 cross 12 complex matrix in Mathematica , I need to work with bigger size matrix of the dimension of the order of hundreds , I was wondering if Mathematica can handle ...
4
votes
1answer
93 views

Solve or preferable Reduce equation

I am new to mathematica and trying to solve and reduce the following: Solve[1 - (1 - p^y)^(u (1 - p)) == a, y] or ...
0
votes
0answers
271 views

Problem with Plot and ParametricNDSolve

This is my first question on this site, I hope it is written in an understandable way. Let's start. My aim is to plot a certain parametric region, with $x$ and $y$ coordinates given by the following ...
1
vote
1answer
88 views

Solve for values which produce negative real Eigenvalues?

Given an n x n matrix "A", with one or more unknown parameters, I'd like to show a plot of which values produce stability (negative Eigenvalues). For example, say you have a simple mass-spring-damper ...
1
vote
1answer
48 views

Problems solving a differential equation

I am trying to solve a differential equation: $dN/dt = a*N*(90-N)$ with $N(0)=3$ and $N(11)=43$: Using: ...
0
votes
0answers
43 views

Solve provides inter-dependent solutions not only variable dependent solutions

I have four implicit equations and trying to find the rest points of a system by using replicator equations. ...
2
votes
2answers
198 views

Solving a system of nonlinear equations 2

Regarding this question: Solving a system of nonlinear equations When I try to solve the same system (with the code proposed in Daniel Lichtblau's answer) with different Right Hand Side values, ...
2
votes
1answer
62 views

Plotting Multiple Solve Functions

My goal is to plot the functions returned from Solve but assigning each solution to a different function. Here is an example where I do it by hand ...
1
vote
0answers
58 views

Help inteprete the solution given by reduce

i am trying to solve for the a2 in the below equation on Mathematica ...
2
votes
1answer
155 views

Problems with NDSolve and partial differential equations of several variables

Suppose we have the following partial differential equation: $$ 0 = \frac{ \partial w }{ \partial \tau } + \left( w + \sqrt{ h + \beta } \right) \frac{ \partial h }{ \partial \chi } $$ where $w$ = ...
1
vote
2answers
115 views

How to solve ArcSinh equation for many differents parameters?

I am totally stuck trying to solve the equation below (1/2) x Sqrt[1 + 4 a^2 x^2] + ArcSinh[2 a x]/(4 a) == d Where a and ...
1
vote
1answer
110 views

handling division by zeros and line equations

today I was writing a code which takes some line equation and a circle equation,finds intersection points that are on $II$ and $III$ quadrants,draw a tangent line to circle from that point and then ...
1
vote
1answer
34 views

problem on returning value of function as a list using if

today i was writing a function for my project using mathematica that gives a line equation in form of $y=mx+b$ and a circle equation in form of $x^2+y^2=r^2$ and finds the intersection point which is ...
0
votes
3answers
93 views

High-Precision NSolve

I need to calculate the intersection of two curves f1[x_] := ((Zl ρ ) Exp[-x]) f2[x_] := (α k e^2 /x^2) Where ...
0
votes
0answers
39 views

Problem with solving an equation [duplicate]

I dont understand why Mathematica cannot solve this equation: Solve[Log[x^2 + 5] + 0.5 x + 1 == 0, x] I get this error message: Solve::inex: Solve was unable to solve the system with inexact ...
1
vote
1answer
161 views

Solving systems of equations

So I have a set of equations like 12 of them but 13 variables. However I would like to find the numerical value of the roots for the maximum value of a particular variable. I don't know how to do that ...
3
votes
4answers
366 views

Solving puzzles with Mathematica

I would like to be able to solve logic puzzles such as the one described here using Mathematica. I have copied & pasted the listed example below to save on jumping about with hyperlinks: The ...