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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0answers
76 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 ...
0
votes
1answer
112 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: ...
8
votes
1answer
189 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
2answers
52 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 : ...
3
votes
3answers
301 views

Solve: Merging two branches of the solution

I have the following code: ...
0
votes
1answer
56 views

using FindRoot to solve 3 simultaneous equations [closed]

I'm trying to solve 3 simultaneous equations derived from an electrical circuit of a common source amplifier. ...
1
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0answers
136 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 ...
0
votes
1answer
95 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 ...
-2
votes
1answer
74 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
137 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) = ...
1
vote
1answer
77 views

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

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
212 views

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

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. $$y = x^x (1-x)^{(1-x)}$$
0
votes
0answers
77 views

How to determine why Solve[] failed?

I don't know what to make of Solve[] failing on this: ...
1
vote
1answer
103 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]}. ...
1
vote
0answers
59 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
2answers
345 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 ...
5
votes
2answers
306 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 ...
3
votes
1answer
163 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 ...
0
votes
1answer
90 views

Problem using NDSolveValue

Good afternoon, fellas. Could anyone here help me solve this problem? ...
6
votes
4answers
330 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 ...
0
votes
1answer
178 views

How to convert a system of parametric equations?

I have a system of parametric equations (t is a parameter) ...
2
votes
1answer
164 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. ...
4
votes
1answer
172 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
80 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 ...
1
vote
1answer
87 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 ...
0
votes
0answers
67 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), ...
2
votes
2answers
150 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 ...
1
vote
1answer
86 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. ...
0
votes
2answers
230 views

NDSolve issue with initial and boundary conditions

While solving the heat equation in one spatial variable $u_t = u_{xx} $ (x goes from 0 to L) with the initial temperature distribution $T_0 \frac{x(L-x)}{L^2}$ , and with neumann boundary conditions ...
2
votes
1answer
83 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} - ...
0
votes
0answers
56 views

Finding common roots to several functions

I am trying to solve the following problem. Given $a\in\mathbb R^n$, $u\in\mathbb{R}^n$, $m\in\mathbb{N}^\star$, Find the/some common roots $(t_1,...,t_m)$ of the $\frac{m(m-1)}{2}$ ...
2
votes
2answers
138 views

A peculiar behavior of NSolve[]

NSolve[Power[x + 1, x + 1] - Power[x, x + 2] == 0, x, Reals] returns: {{x -> 3.14104}} Great. However, ...
0
votes
1answer
74 views

Symbolically solve system of equations involving matrix

I need to solve the following system of equations symbolically for a_i, b_i, and c_i: ...
1
vote
0answers
101 views

Can Mathematica Find Closed-Form Solution this Equation [closed]

I have tries to solve an equation by using Solve[] to find pl as a function of other variables. However, it generates an Error! Can anyone help? ...
12
votes
1answer
135 views

Strange result of Reduce and ForAll

In the question Can Mathematica tell me if a polynomial has all real roots?, quite a few of interesting answers were given. I wanted to add another one, using quantors, and observed some strange ...
9
votes
6answers
796 views
0
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1answer
66 views

Question about the third argument of Solve [duplicate]

I'm learning about derivatives. This is my code: ...
2
votes
2answers
175 views

Study the possible coincidences of the three clock hands hour, minute, and second

Inspired by the very nice problem solutions of the problem of coinciding clock hands, I'd like to extend the question including a "second" hand. While it is obvious that all three hand can coincide ...
3
votes
2answers
360 views

How to solve numerically an equation which contains numerical intergration?

F1[x_] := NIntegrate[E^Sin[y x], {y, 0, 1}] F2[x_] := Log[x] NSolve[F1[x] == F2[x], x] I want to solve the equation, but Mathematica don't solve it. ...
1
vote
1answer
328 views

Solving a complex logarithmic equation

I am trying to solve the following equation for $x$, with integer $n$. (1 - ((-1 + x)^E x^(1 - x) Log[x]^-E)^(1/(-1 + E)))/(-1 + x) == n
-2
votes
1answer
140 views
22
votes
4answers
1k views

Hightlight all the self-intersections of a Lissajous figure

This graph–also known as a Lissajous figure–contains so many self-intersections.How can I highlight them? ...
0
votes
1answer
57 views

Solve and NSolve hitting iteration limit for simple system [closed]

I'm am trying to get Mathematica to determine the intersection of a line and a parabola, like so: Solve[{x + y == 6, x^2 == y}, {x, y}] But evaluating this gives ...
0
votes
1answer
54 views

Question about a catalytic equality?

I have a question on math.SE that explains how I came up with these equations. ...
2
votes
1answer
92 views

Reduce / Solve cannot solve simple equation

Why does Reduce[{a^b*c^b == c, 0 < b < 1, a > 0, c > 0}, c, Reals] give ...
2
votes
3answers
202 views

Find roots of a peak to calculate its width at 10% peak height

I have numeric data points (x,y) values from a peak. I constructed a interpolation to get an interpolating function. Interpolation[data] What I want to do is the ...
0
votes
1answer
50 views
0
votes
1answer
85 views

Recursion depth and solving equations using Solve

I am trying to solve an equation: ...
1
vote
2answers
302 views

How to Fit experimental data with 4D ParametricNDSolve?

Let me first explain the background problem. I'm trying to solve a problem with a projectile motion in 4D such that the position vector is: $\boldsymbol{r}(t)=\boldsymbol{r}[x(t),y(t),z(t)]$ I have ...