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

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1answer
102 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 ...
0
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3answers
100 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
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3answers
104 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
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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
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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
131 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
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3answers
100 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
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0answers
32 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
86 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
31 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
50 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
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2answers
51 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
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 ...
0
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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
49 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
69 views
1
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0answers
37 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 ...
2
votes
2answers
75 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
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1answer
71 views
3
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2answers
89 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
101 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
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2answers
98 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
2answers
72 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
41 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
97 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
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1answer
59 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". ...
0
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0answers
47 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\{ ...
1
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1answer
140 views
2
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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 ...
14
votes
3answers
1k views

NSolve gives additional solutions that don't satisfy the equations!

I am trying to solve the following polynomial equations in Mathematica: ...
1
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1answer
93 views

RSolve works slow and does not give an analytical solution for solving high order linear difference equations

RSolve@@{{a[n]-a[n-10]==101}~Join~Table[a[i+1]==101+10i,{i,0,9}],a[n],n} I want to get the exact form of general formulas, but ...
0
votes
1answer
140 views

How to solve a large system of non-linear equations

I would like to solve Saha equations on Fe, which have 27 unknowns. Saha equations basically give you the ratios of the unknowns, but the unknowns are subject to constraints. What function shall I ...
1
vote
2answers
63 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: ...
-1
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1answer
52 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
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1answer
58 views
1
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1answer
170 views

Solve a system of parametric equations

I have a system of parametric equations (with a total number of 8). I tried to solve this system by using Solve. I have not received an answer after about 4 hours! ...
0
votes
1answer
32 views

Is there a way to have FindInstance or Solve give only positive integer solutions?

I keep getting either negative or super long answers or super long negative answers in no particular order :\ ... Is there a way to only ask for positive solutions? (here we want 0 < x<(10^12+y) ...
0
votes
1answer
106 views
0
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1answer
75 views

How to create a line due to requiriements?

Considering we have three lines, and know the intersection points (How to find intersection points of lines?) How can I draw a line that will cross the intersection point of the two lines and will be ...
1
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0answers
65 views

How to find Pauli matrices

I wanted to find the Pauli matrices, so i wrote down this code: z = {{a, b}, {c, d}} i = {{1, 0}, {0, 1}} Solve[z.z == i, {a, b, c, d}] and mathematica gave me ...
1
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3answers
341 views

How to find intersection points of lines?

Considering I have three functions f1 = -x + 1; f2 = x - 1; f3 = x + 3; How can I find the intersection points of this functions? Thanks. This didn't work ...
11
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1answer
279 views

Does NRoots own an abstract counterpart? If not, can we write one?

We know when solving linear algebra equations, despite its abstract syntax, LinearSolve is much faster compared to Solve: ...
2
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1answer
94 views

Optimizing alphametrics code

First of all, thank you all in this great community. I have been reading a lot of threads about Mathematica optimization learning things like using Compile ...
0
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0answers
141 views

Solving Symbolically Equations with Vectors and Matrices

I want to solve equations with vector variables and vector/matrix parameters symbolically. As a basic example I would like to be able to solve something like $[I-aG]x=b$ where $a,b \in \mathbb{R}^l$ ...
0
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1answer
59 views

How to extract a solution

Is there any way to get the actual number from this? NSolve[x^2 - 5 y^2 == 1, {x, y}, Integers][[1]][[1]] instead of ...
13
votes
4answers
650 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
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0answers
40 views

NSolve can not handle a PolyGamma equation

I would like to solve the following equations numerically: ...