Questions tagged [equation-solving]

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

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2
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2answers
72 views

Why is FindRoot throwing a “singular Jacobian” error when function has small values?

Running the code: FindRoot[PolyLog[2, -E^-(10 + Sqrt[1 + x^2])] == 10^-30, {x, 10}] Gives me the error: ...
0
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1answer
53 views

Solving equation involving an undefined function

I am new to mathematica and this is my first question, so please forgive me if it is something trivial. I am solving a maximisation problem, and my foc is the following: ...
6
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1answer
84 views

Implicit Riccati Equation Solver (to find the anti-stabilizing solution)

I've found that the latest MATLAB icare() solver includes the possibility to find also the anti-stabilizing solution of the Riccati equation. I haven't found a ...
0
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0answers
25 views

Finding intersections of points from more than two functions

How to find the intersections of points for more than two functions? Say I have f1, f2, and f3. I don't want to do : ...
8
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1answer
235 views

Reusing PARDISO symbolic factorization

Is there a way to do this natively in Mathematica? I read in several places that this is possible with LibraryLink, but I don't have a lot of experience with C and so I'm having trouble implementing ...
0
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2answers
37 views

Is it possible to use Reduce in a way that “eliminates” some unwanted variables, and only gives constraints between wanted variables?

Reduce[{x == z, y == z}] gives y == z && x == z but say I'm only interested in constraints that appear between ...
2
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0answers
92 views

Finding 36 integer solutions to a set of 14 equations using various boundary conditions

What is good way to solve this system of equations? I have it run now for quite some time and it does not spit out a solution. ...
-1
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1answer
34 views

Finding the roots of quintic equation

I want to solve my quintic equation with methods Newton and Bisection , and compare them. And I want to know, how to call Nsolve or Roots and told them that they use only for example Bisection ...
1
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1answer
68 views

Solving a system of two equations of cube integers using ParallelTable

Well, I have the following problem: I need to solve the following system of equations: $$ \begin{cases} n=a^3+b^3+c^3\\ \\ n=d^3+k^3+f^3 \end{cases}\tag1 $$ Where: $n\ne a\ne b\ne c\ne d\ne k\ne f$;...
0
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1answer
64 views

Integrating FindRoot

I have a certain function F[a_] := FindRoot[f[a,x],{x,0.5}] and I want to compute NIntegrate[F[t],{t,0,1}]. However, ...
1
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2answers
58 views

Solving a big system of equations using certain conditions

I have the following problem: I want to solve a big system of equations for a certain number of variables which I call $a_k$, the variables need to satisfy the following conditions: all $a_k\in\mathbb{...
3
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1answer
51 views

How to terminating a Do Loop when encounter FindRoot::lstol warning

While finding the roots of a system of non-linear equations, I am encountering the warning "FindRoot::lstol: The line search decreased the step size to within tolerance specified by AccuracyGoal and ...
0
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0answers
21 views

Importing data compared with manual data using FindRoot

The code below as written works fine. The problem I am having is that if a replace "dat22" in the line "lhsp = lhs - dat22[[i]];" by "aps" which is a list with the same numbers but obtained from ...
2
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3answers
144 views

Problem with Fourier Transform output

I am trying to evaluate this FT, but Mathematica takes long time without output ...
1
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2answers
50 views

Approximate solution for ODE

I am trying to find approximate solution for nonlinear ODE(I know there are are ways to do it in mathematica) but I really want why is not working(I modified the code base on some codes suggest by ...
4
votes
2answers
151 views

Why does not ContourPlot provide double roots?

Why ContourPlot does not give double roots? Here is a simple example. ContourPlot[(x-1)^2 (y - 3)^2 == 0, {x, 0, 5}, {y, 0, 6}] If I have a much more complicated ...
5
votes
1answer
94 views

Discrepancy between the results of NDSolve and DSolve (equations related to one step processes)

Bug introduced in 12.0 and fixed in 12.1 The following are the dimensionless equations of a one-step random walk with an "impure" reflecting boundary assuming only four possible states, i.e., n=0, 1, ...
1
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1answer
33 views

NSolve and MemoryAllocationFailure

I have a code like, ...
7
votes
2answers
142 views

DEigensystem gives x-dependent eigenvalues

Bug introduced in Version 11 or earlier and persisting through 12.1. Reported to Wolfram Technical Support as CASE:4532301. I am considering the eigenvalue problem associated with the double-well ...
4
votes
1answer
107 views

Trouble with dependent variables in NDSolve while modelling transparent boundary conditions on a quantum graph with Mathematica

I am trying to create a model of plane wave's propagation on a quantum graph(metric graph with a differential operator, Shrodinger operator in my case, along the edges and continuity condition at the ...
2
votes
1answer
91 views

Calculate this Eccentricity of a hyperbola with Reduce

How to calculate the Eccentricity e? $F_1, F_2$ are the left focus and right focus respectively of the hyperbola:$\frac{x^2}{a^2} - \frac{y^2}{b^2} =1$( a > 0 , b >...
0
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0answers
38 views

FindRoot not recognising replaced symbol in nested function

I have the following example FindRoot function as part of a Nest function. ...
-1
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1answer
45 views

Plane 3D Plotting range values

Below example is equation of a plane example I would know how to determine the range of values for x, y and z respectively. ...
1
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2answers
55 views

How to solve an algebraic equation with InterpolatingFunction?

How to solve the equation f[t]==0 for the function f[t] defined by differential equation,i.e. if ...
1
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1answer
32 views

Solve a system of equations mixing real and integer variables

I'm trying to solve a system of equations and inequalities with 5 variables but one of them is real, and the other 4 are integer. How could I tell this to Mathematica? I tried using ...
2
votes
1answer
53 views

NCSolve - solve for a variable

I use the latest NCAlgebra package (5.0) for non-commutative algebra. << NC` << NCAlgebra` NCSolve[a**x==b,x] How do I solve for the variable x, ...
0
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1answer
56 views

How do I make a function from a solution? [duplicate]

This expression: FullSimplify[Solve[dx == dL - (1/2) dd, dL]] Gives this solution (I've simplified it for brevity): $$\left\{\left\{ d_L\rightarrow \frac{\sqrt{...
0
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2answers
62 views

Series can not expand the following root object about infinity. Is there another way to expand it?

I have the following equation which I want to solve it for r: ...
0
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1answer
27 views

Use the NSolve function on a list of values

Is there a way to have NSolve loop through a list of values? I know how to use it for single values but unsure if I can get it to loop through a list. I want it to loop through my list of p and have ...
0
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1answer
40 views

NSolve produces no solution to a nonlinear system [closed]

This NSolve code on a system of nonlinear equations produces no output: ...
1
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0answers
88 views

NDSolve numerical problem

I am trying to solve a couple of differential equations given by: $$F(H(t))=R(\phi(t))$$ $$\phi(t)''+H(t) \phi'(t)+ m \,\phi(t)=0$$ where $m=1$ and $F$ and $R$ are just particular functions. In ...
1
vote
1answer
65 views

I am unable to solve angle of a trigonometric equation

I am fairly new to Mathematica, so this may be a simplistic question, but I want to learn. I know how to use the Solve function to solve a single equation like this: $$\cos[41.614-x]-1.2752|cos[1....
1
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2answers
42 views

Plotting a complete response to an oscillation; already have particular solution, not sure how to solve for constants in homogeneous solution

I am writing a code that plots an oscillator's response to a periodic excitation. The response consists of the following: x(t) = xh + xp where xh is the homogeneous solution and xp is the particular ...
3
votes
2answers
98 views

Why Mathematica gives me different results depending on the order I set the parameters when I solve this differential equation?

I am asking Mathematica to solve a differential equation using DSolve, with two different parameters, q and m, and then evaluate at a point. So I write the ...
1
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1answer
75 views

How to solve first order complex differential equation?

I want to solve these differential equations and want to get the value of 'a1'. I used this code given below but it is not showing any result. If anyone can resolve this will be appreciated. ...
0
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0answers
42 views

Set of multivarible expressions to be re-expressed a single variable

I have a set of expression such as $\frac{3x+y-z}{6x}$ and $\frac{3 x-y+z}{12 x}$, which can easily get re-expressed as $p$ and $(1-p)/2$, where $p=\frac{3x+y-z}{6x}$, but is there a way to find this $...
3
votes
2answers
70 views

Solving equation for a parallel capacitor

I am a beginner at Mathematica and am trying to solve a simple equation. There are multiple ways to solve this and I am trying to solve this using charge conservation. ...
1
vote
1answer
49 views

How to use output of NSolve for further calculation and than plot?

I am trying to plot the output using these linear equations but finding some difficulty. Here I am using the output of these linear equations and after that using them in another formula and after ...
2
votes
1answer
55 views

Vectorized RootFind for interpolated function

I've spent the last few days trying to vectorize my code to speed up root-finding on a grid. Apologies in advance if my code is poorly formatted. I have a fair amount of setup for the problem. It ...
0
votes
0answers
47 views

Table values of non trivial zeros of Riemann zeta function using integral form

I want to build a table values of non trivial of Riemann zeta function using the following function up to $ 10^4$ zero ,For all $s\in\mathbb{C}\setminus\{1\}$ the integral relation $$\zeta(s) = \frac{...
0
votes
1answer
43 views

Get the representation of {x,\theta} with the given equations

I am working with a Transfer funtion problem. I want to get the representation of {x, $\theta$} with the given equtions(below). In the equation x10 and x20 means the initial value of x1 and x2. all ...
0
votes
0answers
92 views

How to solve these equations without errors?

I'm a new user of Mathematica 12. I have to plot real and imaginary solutions of two equations, eq1 and eq2, which contain the ...
1
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2answers
87 views

Need help in Fourier Transform

My code takes long time without results even with Apart function for this simple function. ...
0
votes
0answers
39 views

Problema simulating FindRoot

I am writing a procedure that simulates the findRoot built-in function using the same code that appears at chapter 6 of $\textit{Programming in mathematica}$ by Paul Wellin. The code is the following....
-1
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2answers
43 views

Eqaution solving & checking program! [closed]

Slove the eqaution 2x^2+5x+1=0 in real number range. Then, by putting it in the equation, check if that is correct. (Use NSlove, Chop, and substitution) I want a code which uses above three ...
0
votes
1answer
62 views

How can I calculate this integral?

I would like to calculate the integral in equation pol[x] if the quantity is positive or negative. ...
3
votes
3answers
77 views

Need help with finding a matrix

Could anyone please help me find a 4 by 4 matrix A such that A.Transpose[A] exactly equals the following matrix: ...
4
votes
2answers
148 views

InverseFourierTransform takes forever

I am trying to find InverseFourierTransform of the following function, but the code below does not give me a result. I do not get any error messages but the calculation just does not end. Any Help? ...
0
votes
1answer
37 views

Assign variable to solve [duplicate]

I would like to assign my result from equation. I tried /. and := but it gives me empty variable. How can i fix it?
0
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3answers
75 views

System of non-linear equations - Symbolic solution

I've been running this code for more than 12 hours and still can't find a symbolic solution for this. Maybe there is a way to simplify it or something might be wrong with the code. Do someone have a ...

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