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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2answers
25 views

Finding intersections of two parametric curves

I am dealing with the root finding of two parametric data curves (data below). I have already checked Parametric Interpolation of 2D data, which I found useful for plotting, though it is not adequate ...
3
votes
3answers
199 views
0
votes
0answers
17 views

NSolve running for ever

I have troubles running NSolve for my physics problem. I am new to Mathematica, which is why I might be missing some key solutions. I have the following function with the variables: ...
0
votes
0answers
33 views

Solution Branch Switching of Quartic

Im using a closed form solution for quartic equation. In the quartic equation, there are parameters that are being varied and therefore the solution changes depending on these parameters. The ...
3
votes
0answers
165 views

Nonlinear FEM and FindRoot

I'm trying to develop a kind of nonlinear FEM application using mathematica to solve a bvp like the following: $$ \gamma(u') ~u^{iv} + 2 \gamma'(u') u''' u''+ u''^3 = f(x) $$ where $u = ...
0
votes
1answer
59 views

Solve seems broken after I installed the package Tomatlab.m

After I downloaded the Mathematica package ToMatlab.m, Solve does not work as before: ...
0
votes
2answers
38 views

Selecting the maximum value from the results returned by NSolve

I'm trying to select the maximum value from the answers Mathematica 7.0 is getting from a simple basic NSolve algebric equation : ...
5
votes
0answers
42 views

Using a Mathematica index as a DiscreteVariable in NDSolve when solving a coupled set of ordinary differential equations

Context Since the explanation below of the problem to be solved is lengthy, let me preamble this by saying that I have code that works to solve the problem, but I don't know whether (1) it's ...
0
votes
1answer
77 views

A question about calculus and Programming

I am a very new user and I would like to know how to calculate the following operations in Mathematica. Honestly this is not a homework. I am an french architect and I would like to be back in Math ...
1
vote
0answers
52 views

How can I improve the solution of my PDE?

I want to improve the last code to find a better solution for umi. For now I'm using only MaxStepFraction. Also, when I put no ...
-1
votes
0answers
57 views

Solving a system of equations using NSolve [on hold]

I am trying to solve the following system of equations using NSolve, but am running into some problems. Any suggestions ? CASE1 - Facing Problem in Solving the ...
0
votes
1answer
40 views

using FindRoot to solve 3 simultaneous equations [on hold]

I'm trying to solve 3 simultaneous equations derived from an electrical circuit of a common source amplifier. ...
0
votes
1answer
97 views

Eliminating parameter from parametric equation

In Mathematica Online I tried: Eliminate[{x == t + t^3, y == t - t^3, z == 1 + t^4}, {t}] ...
-2
votes
1answer
57 views

Sign of a symbolic expression as a function of parameter values

I need to know the sign of the following expression for p[t] = z/(1-a), as a function of the parameters {a, b, c, z}: ...
1
vote
1answer
70 views

Hill function (equation) vs a gene

So im trying to make one equation equal another to solve for all physically realistic values of $X$. Hill function is: $$ F(X)=\frac{1}{1+(\frac{X}{K})^n} $$ and Gene Z equation is: $$ Z(X) = ...
0
votes
0answers
30 views

Generating vectors with restrictions on a lattice

Suppose we are given a certain adjacency matrix that contains the information for a given lattice. I want to generate a configuration of vectors that satisfy a restriction. Specifically, if I have ...
0
votes
0answers
53 views

NSolve can not handle a PolyGamma equation

I would like to solve the following equations numerically: ...
1
vote
1answer
52 views

Trying to find solution for system of ordinary differential Equations [on hold]

I've got 2 functions: A'[t] = (0.5/(1 + (B/k1)^n)) - 0.2*A B'[t] = (1/(1 + (A/k2)^n)) - 2*B with conditions of ...
0
votes
0answers
15 views

Recurrent equations [duplicate]

I want to make a relation to show the first 7 elements that don't have the number 7 in it. So far i know how to make it to show the first 7 elements with RecurrenceTable[{a[n + 1] == 7 a[n] + a[n], ...
5
votes
1answer
159 views

Solution to $y = x^x (1-x)^{(1-x)}$ for $x$ [on hold]

Does anyone have any insight to a symbolic Mathematica solution to this equation for $x$ in terms of y? Symbolic of any sort, just not numeric. $$y = x^x (1-x)^{(1-x)}$$
6
votes
2answers
176 views

How to read complicated result from Reduce?

How can I read this Reduce output from Mathematica that I got from solving an inequality? I do not perfectly know when one case in this case analysis is over and ...
11
votes
3answers
452 views

How can we plot the complex roots of an equation?

If we'd like to display the $n$ roots of a polynomial on the complex plane as points, how can we do this? For example, if we have the equation $x^3 + x^2 + x + 1$, how can we plot the 3 roots as ...
0
votes
0answers
66 views

How to determine why Solve[] failed?

I don't know what to make of Solve[] failing on this: ...
21
votes
1answer
786 views

Bug in Solve (Mathematica 9)

The issue seems to be fixed as of Version 10.1. Just came across the strangest bug under both Mathematica 9.0.0 and 9.0.1. If one enters: ...
1
vote
1answer
88 views

Defining Solutions to FindRoot a functions of parameters-Part II

Here's a similar question as the the preceding question with the same title, but this time with vectors, which I need to use. I followed the suggestion in the answer the the previous question, but it ...
1
vote
1answer
73 views

How to speed or help Solve[] when it is stuck?

The code below generates a system of equations that I need to Solve[] for {c[5], c[6], c[7], c[8]} in terms of {c[1], c[2], c[3], c[4]}. ...
14
votes
2answers
430 views

Determining the default Method used in optimization and root-finding algorithms

Is it possible to extract the Method which is used in functions like NMinimize, FindRoot, ...
0
votes
0answers
38 views

NSolve Duration for simultaneous equations solving

At the moment I am asking myself why mathematica gets to point of needing enormous amount of time to solve equations like these when one more "row" or "colum" or both was added in this equations ...
0
votes
0answers
79 views

Finding the numerical solution to a polynomial of a high degree [closed]

I would like to numerically solve the following equation for ρ and use the obtained values of ρ to calculate the values of VR ...
0
votes
2answers
325 views

Does the equation have two roots? [closed]

I want to solve the equation $$-x^2+\sqrt{2-x^2} \left(x^2+2 x-1\right)+2 x+5=0.$$ I tried ...
12
votes
2answers
291 views

Behavior of Reduce with variables as domain

When using Reduce, I accidentally put a set of variables as the domain. To my surprise, it not only seems that Reduce expects ...
3
votes
1answer
93 views

Roots of Whittaker W function

I am interested in finding the roots $u$ of the equation $$ W_{1,\imath b}(a)=0, $$ where $W_{\kappa,\mu}(z)$ denotes the Whittaker $W$ function, $a>0$ is a fixed parameter, $\imath=\sqrt{-1}$ and ...
6
votes
4answers
148 views

How to eliminate variables when using Solve[]

In certain problems, we need to solve systems of equations and get results in terms of just selected variables. For example, how could we solve eqn==0 below for ...
3
votes
2answers
96 views

Solve for x given an interpolation function, y

Given a list of data, lst={{x1,y2},{x2,y2},...,{xn,yn}} and the interpolation function fun, y=Interpolation[lst] which ...
0
votes
1answer
63 views

Problem using NDSolveValue

Good afternoon, fellas. Could anyone here help me solve this problem? ...
13
votes
4answers
693 views

How to make a Line[] with no end?

I'm trying to do this: In this graph, the secant points are aproximated in order to become the tangent, it seems I need some kind of function which plots a line based on two points and it's points ...
0
votes
0answers
37 views
0
votes
0answers
42 views

Solving a nonlinear equation involving convolution

I consider the following functional : $\psi(u,v)= -u(1-v)(1-\alpha k * v) + \epsilon v (\alpha k * v)$, where $k(x)$ is a smooth kernel with $\int |k| = 1$ and $\int k_+ = \alpha \in ]0,1[$, $u(x), ...
7
votes
4answers
682 views

How many times do the two given curves intersect at the origin?

I'm reading/studying on my own a book about algebraic curves. I'm trying to find a way for Mathematica help me with the following (the book, ISBN: 038731802X, allows me to use any CAS / program. ...
0
votes
1answer
106 views
2
votes
1answer
106 views

Solving an integral equation numerically

my problem is: I get the result of definite integral and now I need to find the upper limit for the same integral but with opposite sign value so f2=-f1. ...
1
vote
1answer
75 views

Why can Reduce solve for Integers but not for Reals?

I'm showing as an image, since the question is generic. If we remove $m$ from the inequality we get both solutions. Why doesn't the first inequality work for both domains? Edit here is the code per ...
4
votes
1answer
145 views

Does `Reduce` give complete and necessary conditions?

I want to obtain a solution for a system of five inequalities. For instance, ...
1
vote
1answer
65 views

using FindRoot with a Module that takes a parameter

Observed an error when calling a Module from FindRoot. I created a module which first solves a differential equation and then returns the value of that differential equation when the independent ...
1
vote
2answers
80 views

Plotting the solution of a cubic equation against a coefficient in the equation

I have to plot the solution of the following equation against the coefficient $L$. Since it's a cubic equation, I'd like to filter out the real solution first and plot that then. The equation is $L ...
0
votes
0answers
27 views

How to refine the approximate solution of an implicit function? [closed]

I have an equation of the form exp(A(C-x))-1-exp(x-B(C-x)^(2/3))=0 Here A,B and C are constants, x is the unknown, I want to find, but approximate value of x is known. so, the problem is how to get ...
1
vote
1answer
74 views

Is it possible to solve a certain set of nonlinear equations in Mathematica?

I read this question in a Chinese forum last year. At the end of the discussion, they provide a solution of the equations from a C++ program. Unfortunately, they did not get the right answer. ...
4
votes
1answer
152 views

What are the hidden specifications for FindRoot

The Help page of FindRoot says: "by default, FindRoot uses Newton's method (Newton-Raphson) to solve a nonlinear system" (or a nonlinear equation I ...
2
votes
1answer
50 views

Plot directional field with a initial vlue

I do not have enough reputation to comment on other questions, hence I have to ask my own one I want to solve the following nonlinear first order ODE, $$(1 + x) (0.5 y[x]^{-0.5} (x - y[x])^{0.5} - ...