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

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-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
45 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
46 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
27 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
44 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
61 views

Fixed Points Problem with 2D Mapping

I have been playing with the mapping given by ...
1
vote
0answers
31 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
62 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
69 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
68 views

Elimination returning true instead of correct answer

I define the following functions: ...
3
votes
2answers
79 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
vote
2answers
93 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
36 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
62 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
40 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
93 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
42 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
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". ...
1
vote
1answer
137 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
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: ...
0
votes
1answer
62 views
-1
votes
1answer
48 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
56 views

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

I have a series of analytical equations: ...
0
votes
0answers
64 views

Regarding equation simplification [on hold]

I have 2 variables, M and L. M == x y(z-k)^2 (2z+k)π / (3z^2) L == x y(z-k)(z+k)π / z^2 Is it possible to perform a simplication in Mathematica, such that I ...
0
votes
1answer
28 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
0answers
77 views

Implicit/Backward Euler method [closed]

I'm trying to solve (and plot) a differential equation using Explicit Euler method and Implicit Euler method. The Implicit method worked out jst fine but I have problems with Implicit one... I made ...
1
vote
0answers
61 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 ...
0
votes
1answer
71 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
vote
3answers
322 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 ...
0
votes
1answer
130 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
1answer
166 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
57 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 ...
0
votes
0answers
107 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
votes
0answers
38 views

NSolve can not handle a PolyGamma equation

I would like to solve the following equations numerically: ...
1
vote
0answers
88 views

Mathematica reading my mind - Solve knows which variable to solve for

I was checking some of my algebra with the following code; ...
0
votes
1answer
96 views

How to put a condition in 3d plotting

I have the following plotting question: First I want to have 3D plot of Alpha respect to different values of p and l when we ...
0
votes
1answer
58 views

WhenEvent for space variable

Can I use WhenEvent for space variable? For example ...
-1
votes
1answer
95 views

How to get a 3D plot of from the the solutions of function [closed]

I have the following equation: (1 - x)^2 + T^2/((f[x] - L)*(f[x] - L - 2*T))*(P/(N-R+S)) == 0 f[x] = (x*r*(T + L) - T)/((x*r) - 1) ...
0
votes
1answer
62 views

Plotting results of a NSolve problem

I am calculating, numerically, the zeros of a determinant. a1 and a2 are constants, q is a parameter. I would like to vary q and find the roots w as a function of q and plot roots w vs. q. All ...
0
votes
2answers
131 views

How to write Newton-Raphson module and return a value?

I am writing a code which solve nonlinear algebraic systems via Newton-Raphson algorithm. I want to make a Newton Module with another file and use the Module in my test file, but i didn't achieve it. ...
10
votes
1answer
255 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: ...
3
votes
3answers
169 views

How to solve the equation $A \sin x + B \cos x = 0$ for all $x$?

I have the equation: $A \sin x + B \cos[x] = 0$ that should be satisfied for all the $x$. Of course, the solution is obvious: $A=B=0$, but I need Mathematica to resolve it automatically because this ...
2
votes
2answers
79 views

How do I get all the roots within a certain range for an equation? [duplicate]

I wish to find ALL the roots of the following equation $ x \tan(ax) - c = 0$ within a range, where a and c are constants I control. I've been using ...
1
vote
1answer
184 views

NSolve fails to solve a nonlinear equation

Mathematica can not solve this: g = 9.82; ω = 0.5; h = 5; y0 = 1; v = 0; τ = 0; NSolve[h + v t - (g t^2)/2 == y0 Sin[ω t], t]; The error code is: ...
1
vote
1answer
75 views

NSolve on bounded domain

I don't expect NSolve[] to be able to obtain all solutions in generalfor example. In principle there should be an algorithm that finds all solution to $f(x)=0$ for ...