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

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0
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1answer
48 views

FindRoot over a function with some constant variables

I would like to perform the FindRoot command over the function func. Suppose: ...
0
votes
0answers
82 views

Finding roots by solving its ODEs [duplicate]

Roots of fluctuating function (p,q real) needed to evaluate eigenvalues of $$ y(x) = \dfrac{\sin px }{p} + \dfrac {\sin q x }{q} =0 ...(1*) $$ form a real and complex infinite set. The way to ...
1
vote
1answer
89 views

Iteration convergence of Newton approximations

I am trying to determine for which initial values Newton's approximation of specific functions (EX: f(x)=x^2 -1)converge and to what numbers it will converge to. *Where Newton's approximations are ...
0
votes
0answers
66 views

Solve Lagrange-multliplier with arrow-security prices with nonlinear (exp) utility function

at the moment I have successfully solved the Demand function for securities in the following model: t=0 current time, 2 uncertain states with same probability in period 2 indexed with i=1 and i=2. ...
1
vote
1answer
187 views

Why won't mathematica solve my two simultaneous equations? [closed]

I'm trying to solve for two unknowns with two equations as follows; ...
3
votes
0answers
90 views

Finding all zeroes - mysterious missing roots

Finding all the roots of a function of one real variable has been discussed extensively in e.g. Find all roots of an interpolating function (solution to a differential equation) (answer no. 2 by Jens ...
1
vote
1answer
108 views

Quantum Physics question [closed]

I'm not sure if anyone here would be able to help me. But if you know a more appropriate place where I could ask for help, please let me know. So here's the question: And here's my attempt at ...
1
vote
0answers
71 views

Using Solve without introducing extra variables

First post here. I've tried searching for an answer for this for a few days now, but it seems the search terms (solve, slot, etc) are too generic to be helpful. I'm struggling with understanding how ...
0
votes
3answers
102 views

Delay difference equation

How can I correctly specify and solve a system of delay difference equations in mathematica similar to NDSolve with regard to delay differential equations? For example if I want to "see" the values ...
0
votes
1answer
51 views

Using FindRoot in a Table of Iterations [closed]

So I have a tanh curve and a straight line that cross at the point: msol=FindRoot[Tanh[x] == (T/Tc03) x, {x, 1}] This gives me the roots that I need at a certain ...
0
votes
1answer
47 views

Integrate equation. Variable in terms of another

This might have an easy solution but I am new in Mathematica. I have an equation for which I want to find the solution. My equation goes like: $$\frac{dr}{dx} = ...
0
votes
3answers
113 views

How do I solve for the roots of $\sin(x) - x^2=0$? [duplicate]

I have defined h[x] := Sin[x] - x^2. When I submit Solve[h[x] == 0, x], Mathematica tells me Solve::nsmet: This system ...
0
votes
1answer
87 views

solving PDE with periodic boundary conditions

I want to solve a 2D-PDE that has the form ...
0
votes
0answers
73 views

How can I solve this expression?

I'm trying to solve this expression for A, but I'm not sure how. ...
-1
votes
1answer
47 views

how to write out this equation on Mathematica? [closed]

I have this equation that my manager would like to use on Mathematica, but I've only been learning how to use Mathematica for a few hours. I need to solve for Ax and also plot a graph. Please ...
3
votes
1answer
137 views

How to solve a transcendal equation

I want to get the solution x of this equation a (-(1/(1 + b c + a x)) - Log[b c + a x] + Log[1 + b c + a x]) - d = 0 in ...
2
votes
3answers
101 views

Solving equation containing Erf expressions

Given the equation below, how do I find the value of b so that the function is equal to 21. I tried solve but I keep getting an error message. ...
0
votes
0answers
36 views

NDSolveValue:dsvar error in a system of non linear differential equations generated using a Table

I have a system of 4 non-linear differential equation, that I generate using Table command. On solving, I keep getting a dsvar error that is not going away. I debugged my code and figured it has to do ...
5
votes
2answers
93 views

Initial time as parameter in ParametricNDSolve

I need a help with the function ParametricNDSolve. My goal is solve the equation \begin{array} &&\dot{x}(t) = y(t) \\ &\dot{y}(t) = x(t)-1-\varepsilon Cos(\omega t) \\ &x(t_0) = x_0\\ ...
-2
votes
1answer
32 views

Solver for X - with a function [duplicate]

Sorry but I cant figure this out, Someone gave me some help on here yesterday but they didn't show their working so I could not redo what they did when my equation changed. Can someone please help me ...
-2
votes
1answer
56 views

Solve For X inside arc-cos function (with division) [closed]

Very basic but I've been stuck for more than 12 hours trying to solver this equation 20=360/(arccos(X/3200)*2) Can anyone solve X? and explain what exactly you ...
0
votes
2answers
60 views

Nonlinear matrix equation solving in Mathematica

is it possible to solve below equation in Mathematica? A.X+B.Exp[X]==C A, B are square ...
0
votes
0answers
30 views

FindRoot[rhs==lhs, {x,x1,x2}] Vs FindRoot[rhs==lhs,{x,x1}]

What is the difference between these two commands: FindRoot[rhs==lhs, {x,x1,x2}] and FindRoot[rhs==lhs,{x,x1}] They give ...
0
votes
3answers
55 views

Solving system of equations with complex numbers [closed]

I have two equations and two unknowns. The coefficients are complex. How do I solve them using matrices? Or any other method? Here is an example: Trying to find X and Y ...
2
votes
1answer
76 views

Fixed Points Problem with 2D Mapping

I have been playing with the mapping given by ...
1
vote
1answer
58 views

Trouble using Solve and NSolve with functions involving Erf

I have the following functions: R[k_, x_, t_] := -.5*(k - x)*(1 + Erf[-(k - x)/t]) L[k_, c_, x_, t_] := .5*c*(k - x)*(1 + Erf[(k - x)/t]) I'm interested in ...
0
votes
2answers
67 views

Help Solving A Recusive System: “$RecursionLimit::reclim: Recursion depth of 256 exceeded.”

Was wondering if anyone had any tricks/ideas on solving this system of recursive equations I have. Essentially my goal is to have J2 equal to zero, but to understand how tweaking several parameters ...
2
votes
2answers
79 views

Series expression of a Root object

I was wondering if it is possible to get Mathematica to return a series approximation of a Root object. Example: I want a series representation of x in terms of ...
1
vote
1answer
73 views

Elimination returning true instead of correct answer

I define the following functions: ...
3
votes
2answers
94 views

Numerical root-finding: Find leftmost root in a domain

This is surely a duplicate, but I cannot seem to find a similar question. I use NDSolve to find an InterpolatingFunction y[t] ...
0
votes
1answer
109 views

Solving Integro-Differential equations

I need help solving this equation. Is there a built in function that solves this type of equations? DSolve wouldn't work. Updated equation: ...
1
vote
2answers
101 views

Solving matrix equation

How can I solve the forward equation S[t]=C+A*S[t+1]*(Inverse((I-B*S(t+1)))*A for t=1 to t=10 and ...
0
votes
1answer
56 views

Elements inside arrays seem to be strings rather than signed numbers

When I have code like b = Array[Subscript[be, #] &, {3, 1}] b = b /. {Subscript[be, k_] :> Subscript[-be, k] /; k > 1} I am noticing that Mathematica ...
0
votes
2answers
80 views

Why does Solve give a wrong solution to an equation? [closed]

I have got a following equation: -(c - x)/Sqrt[b^2 + (c - x)^2] + x/Sqrt[a^2 + x^2] == 0. Trying to solve it for x, so I evaluate ...
0
votes
0answers
43 views

Solve system of equations derived with the Lagrange approach

I am new here and hopefully you can answer my question. I have to pictures attached. The problem is as follows. I have 4 system equations, derived with the Lagrangian approach. Now I want to ...
3
votes
2answers
104 views

Finding solutions at non-differentiable points of a numerical function

Let's consider a 2D function we can evaluate numerically, but which is opaque to symbolic manipulation (this is just an example): ...
0
votes
0answers
48 views

Why does Mathematica not restrict the domains of Rational Expressions?

As taught in High School Mathematics: $$\begin{array}{ccl} \left\{ {(x-3)(x+3)\over 5(x+3)} : \ x\ne -3 \right\} & \ne & \left\{ {x-3\over 5} : \ x\in\mathbb{R} \right\} \\ \left\{ ...
0
votes
1answer
60 views

Problem in evaluation of a solution and plotting

I've written out a code which solves a equation and uses this solution to find "ph". ...
1
vote
1answer
148 views

Singularity on a simple Plot

While solving quartic equation ...
2
votes
1answer
99 views

Find tangency of InterpolatingFunction and circle

I am trying to use a system of equations to solve for the common tangent of a (polar) InterpolatingFunction and a circle. Unfortunately, both NSolve and FindRoot don't yield results, even when I ...
0
votes
1answer
72 views

How to obtain a convergent solution iteratively for a linear system of equations

I am working on a problem that requires an iterative procedure to solve a linear system of equations, the system of equations in matrix form is: $$\underbrace{\begin{bmatrix} r_{11} & r_{12} ...
1
vote
2answers
64 views

Finding roots of a function with a varying parameter

So I'm brand new to Mathematica, and basically what I want to do is find the roots of a function at varying time intervals. The function I'm using is: ...
0
votes
1answer
69 views
14
votes
1answer
732 views

Is Mathematica `ContourPlot` function really so efficient?

I wanted to find the roots of the function $f(x,y)=\sin(3.2x)\sin(1.3y)-2.1 \sin(1.3x)\sin(3.2y)$. This is what the function looks like: ...
-1
votes
1answer
55 views

How to assign variables to selected roots of a polynomial equation? [closed]

I have a polynomial equation like the below, and I want to assign variables to the roots that are not pure imaginary. How I can do this? ...
1
vote
1answer
63 views

How to change the expressions in terms of a specific variable?

I have a series of analytical equations: ...
-1
votes
1answer
74 views

Define a function and then integrate and plotting of the solved function [closed]

First I want to solve for $n_{0}$ for a fixed value of $n$, lets say $n=1$ $$ n= n_{0}+ \dfrac{1}{2}\int_{-1/2}^{1/2}dq\left(\dfrac{e_{q}+Un_{0}}{\hbar\omega}-1\right) $$ where $e_{q}=2[1-cos(2\pi ...