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

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6 views

Can't NSolve system of exponential and linear equations in several variables

At the moment I am stuck with the following code, when specified to use root , quadratic or log utility functions all it fine, only exponentials like: $\small \left\{-e^{-c_{0,1}}-0.25 ...
0
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0answers
24 views

Solve equations for derivatives

I want to solve some equations in General Relativity numerically with the Runge-Kutta method. Therefore, I need to solve for example $r^{''} \left(\tau\right) + t\left(\tau\right) + a = 3 $, where $ ...
0
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0answers
41 views

Computing the coefficients for Gaussian integral

I wrote a small script to find the Gaussian integral points and weights: ...
0
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0answers
73 views

NSolve and Loop - getting error that does not occur with single instance

I am having difficulties getting this code to work. Code: ...
0
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0answers
44 views

Plot zero contour of a function of two variables

I have F[x_,y_] = f(x,y). I would like to solve (numerically) F[x,y] == 0 to give x as ...
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0answers
47 views
1
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1answer
49 views

Computing a recurrence table backward

I am trying to understand how to compute a recursive equation backward say n = 10 to n = 1. I am trying to solve a PDE for which ...
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0answers
20 views

Solving (one variable) Linear Equation by Dividing Slope by Constants Accumulation? [migrated]

I've been Google searching for this, and apparently my Googlefu is not strong today, or I'm doing something wrong. I have been told that it is possible to solve a one variable linear equation by first ...
0
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1answer
146 views

Usage of Piecewise/RSolve to solve an equation based on condition

`Function optval(vol, intrate, expn, payoff, strike, Etype, NAS) ReDim S(0 To NAS) ReDim vold(0 To NAS) ReDim Vnew(0 To NAS) ReDim Dummy(0 To NAS, 1 To 3) ds = 2 * strike / NAS dt = 0.9 / vol / ...
1
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1answer
64 views

Solve system of equations with implicit function [on hold]

I am trying to solve a system of 3 (non-linear) equations with two variables $x,\ y$ and one unknown function $f(x,y)$ of these two variables. Also, the system includes the change of this function $f$ ...
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3answers
72 views

Getting a list of x coordinates of intersection points of two functions

I have two functions, f[x_] := 5 Sin[2 x] g[x_] := (5 x + 2)/(x + 2) I am trying to find the x coordinates that intersect ...
0
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0answers
35 views

Deciphering output messages using Solve

I'm trying to solve the following system. The error messages I'm getting suggest that there may not be a solution [my desired result], but I'm not sure if there could be something else going on. The ...
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0answers
38 views

How to speed up geometric Resolve query involving $\exists$ and $\forall$?

I would want to test connectedness of semialgebraic sets with naive code like this: ...
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0answers
36 views

RSolve with two variables

I want to find $a(m,n)$ with $~a(m,n)=\alpha * a(m-1,n) + \beta * a(m,n-1)$, where $\alpha$ and $\beta$ are constants. I expect an explicit $a(m,n)$ represented by $a(0,j),~j=1,2,\cdots,n$ and ...
0
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0answers
30 views

Command Select returns empty result [on hold]

I'm trying to do something like c = N[Solve[14 == 3x^2+4x+1, x, Reals]] Select[c, 1 < # < 2 &] Unfortunatelly, I get ...
0
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1answer
47 views

DSolve not outputting any result

I'm trying to solve a system of differential equations using DSolve, but I am not getting any output beyond a repetition of my input: ...
0
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1answer
59 views

Manipulate Solve

I have seen similar questions and answers but it did not help me. I would like to see effects of three constants in equations resulted from solve command. conditions are ...
1
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0answers
28 views

Tracking solutions over a Brillouin zone

Thanks to @bbgodfrey I have a function that finds the two solutions to a set of equations bounded by a hexagonal region (corresponding to the Brillouin zone). It takes the angle ...
5
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2answers
130 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 ...
0
votes
1answer
76 views

RSolve with integrations

I want to solve this question with Mathematica. $$T_0(t)=c(t),\quad T_n(t)=a\int_0^t T_{n-1}(s)\, \mathrm{d}s+b(t).$$ Is it possible to solve $T_n(t)$ with ...
0
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1answer
63 views

Add assumptions to Solve command

I want Mathematica to solve the following by assuming the part within the Log function, which is ...
0
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0answers
64 views

Difficulty solving an equation involving a couple of different powers

I have this semi-complicated equation to which I want to find an analytical solution for $\epsilon$. The equation is a s following: $$a^2 (2 b k \epsilon \sqrt{1 - \epsilon^2/b^2} - 2 c k ...
0
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1answer
67 views

Equation solving problem [closed]

I have this code: ...
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0answers
53 views

I made my own equation, how do I know if it already exists? [closed]

I made my own equation after playing around with some numbers. So I started to look for the equation to be sure I made it first. I googled and searched for it almost everywhere but couldn't find it. ...
0
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0answers
25 views

Convert the output of solve into equality [duplicate]

I know this is has been asked before but seriously, none of the ones I checked helped because they referred to a single variable assignation. Apologies if this is a duplicate. I have many variables ...
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1answer
119 views

Formatting an equation: X^Y to pow(X,Y)

I am trying to solve for the intersection of two circles with arbitrary centers and arbitrary radii. ...
0
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1answer
62 views

numerically solving

I am trying to solve for [Lambda] as a function of a (unknown) from this expression ...
0
votes
1answer
44 views

Setting the solutions of an equation as a variables [closed]

This is probably a simple question, but i couldn't find a solid answer. So i have an equation Solve[{F[x, y] == 0, G[x, y] == 0}, {x, y}] but i want to use the ...
1
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3answers
79 views

Finding roots of transcendental equation and collecting into a list

I am working on a physics reserach project for school and I have run into some troubles working Mathematica. I am a fairly inexperienced mathematica user so any help would very much be appreciated. I ...
6
votes
2answers
164 views

How to reverse irreversible function in Mathematica?

How to reverse formula $y(x)=x (\frac{1}{sin \frac{\pi x}{2}})^\alpha$ i.e. express it as $x = x(y)$ in Mathematica? I did this way ...
1
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2answers
51 views

RegionPlot after Reduce

I have a problem in this form To solve this I have tried this f1[y_] := 2 - (y - 1)^2; f2[x_, y_] := x + 1 - (y - 2)^2; f[x_, y_] := Max[f1[y], f2[x, y]]; The ...
3
votes
3answers
110 views

Reduce gives wrong solutions

Given the follwing system of equations eqs = { x/(x - 2) - 4/y == 1, x/(2 + 1/y) == y/(3 - 1/x) } Although the domain of this system does not contain ...
-2
votes
1answer
52 views

Solving fifth order polynomial equation [closed]

I am trying to solve this equation: 1/s^3 + 3s^2 + 4s + 1 But I am not able to solve it. A little help would be appreciated. P.S: I am new to Mathematica and I ...
2
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1answer
61 views

Faster variant of Reduce for finding zeros of holomorphic functions in a region

I'm currently using Reduce to find zeros of a function in a region on a complex plane: ...
4
votes
1answer
51 views

Sequential System of Equations

I’m trying to set up this system of equations that sequential feeds into itself. I have these 2 equations I’m running. I’m new to Mathematica so I have no idea how to even start this. The basic idea ...
0
votes
1answer
51 views

Roots of a transcendental equation

I need to find the 50 first roots of a transcendental equation. I use Table and FindRoot, so I find repeated positives and negatives values in a list, but I want only the 50 first positives and ...
0
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0answers
61 views

First Order Conditions

I am new to Mathematica so I am not sure if this is correct. I have setup up a Lagrangian and I am trying to get the FOCs of this problem. However, it does not seem to work. Any help would be much ...
0
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0answers
128 views

Solve doesn't solve my transcendental equation

I want to solve a geometry problem. To do this, I need get formula for "d" in the equation: ...
1
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1answer
75 views

Improving Performance - Finding Polynomial Roots [duplicate]

I'm fairly new to Mathematica. In the past, my usage has mostly been limited to solving the occasional equation, making some plots, and working with small scaled statistics. None of these have been ...
0
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0answers
67 views

What does it mean when FindInstance returns unevaluated?

According to the documentation, FindInstance[] return the empty set when it does not find a solution and one of the examples claims that this is proof that no solution exists. So if FindInstance[] ...
-2
votes
1answer
47 views

Solve on parametric equation produces inequal results

I have a parametric (parameter t) equation in two dimensions (vectors). s = Solve[pt[t] == qt[t], {a, b}] Both pt and qt are parametric lines using a and b as ...
0
votes
1answer
109 views

Time evolution of a wave packet from the time-independent Schroedinger equation [duplicate]

Starting off with the time-independent Schroedinger equation (TISE) $\quad \quad -\frac{\hbar^2}{2m} \nabla^2 \psi + V(r, \theta) \psi = E\, \psi,$ I would like to study the time evolution of an ...
0
votes
2answers
39 views

Expand “hierarchical” system of equations

I have a system for equations that is structured hierarchically: - Level 0: these are base variables that I can measure from a process (e.g. a,b,c) - Level 1: these are variables derived from Level 0 ...
1
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1answer
111 views

Approaches to solving non-linear systems of equation with assumptions

The specific type of system looks as follows: \begin{align} (r-r')x+4d_1 x^3+4d_{12}xy^2 &= 0 \\ (r+r')y+4d_2 y^3+4d_{12}yx^2 &= 0 \\ \end{align} Where $r,r',d_1, d_2, d_{12}$ are all real ...
0
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0answers
47 views

No solution for a system of equations

I am a newbie in Mathematica and I face a problem in my attempt to solve a system of equations. The system is the following: ...
1
vote
1answer
157 views

How to plot the graph of the equation F[x,y]=0 if y is real number, x is complex? [closed]

I have an equation F(x,y;a,b,c,...)=0, where x and y are variables, a,b,c,... - parameters. y is a real number, x - complex. For every given y I need to solve this equation, i.e. to find Im(x) and ...
1
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1answer
78 views

Solving equations bounded by a region

Straight to the point I have a function ...
0
votes
1answer
32 views

Strange behaviour of Append [closed]

I have the following situation and I completely do not understand why the second system can be solved but the first (of the same equations, as it seems) cannot. How is it possible? ...
0
votes
0answers
26 views

Problem evaluating function

Hey there I am missing the trick in evaluating following problem so that mathematica first solves the derivative of the legendre polynom and just after that it solves the whole thing for value 1 ...
0
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1answer
24 views

Many NSolves to interpolating function

I have an expression of the form: expr = TerribleNumericalFunction[U[p]] == SimpleFunction[p] The Simple function is a ...