Questions tagged [equation-solving]

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

Filter by
Sorted by
Tagged with
0 votes
0 answers
40 views

Inner working of `NDEigensystem` [duplicate]

What is the inner workings of the NDEigensystem? How does it solve a second-order differential equation? I know it is an inbuilt Mathematica function. I want to ...
user444's user avatar
  • 2,126
0 votes
0 answers
56 views

Solve constraints don't work properly

So in my previous question, I was trying to find two parameters kV and km for an implicit function using FindFit(FF) command and I did it but the problem is that it takes around an hour to do it. ...
Karen Simonyan's user avatar
0 votes
1 answer
81 views

Is this a bug in FindRoot?

I am computing large numbers of zeros of RiemannSiegelZ. It is easy to bracket a root with sign changes, so I am using Method->"Brent". I observe the following: ...
stopple's user avatar
  • 1,141
5 votes
1 answer
194 views

Colouring Bifurcation Diagram

I need to plot the bifurcation diagram for the function given below. g[x_, r_] := 6 x^2 + r x^4 + x^6 Plot[g[x, -4.9], {x, -2, 2}] Bifurcation Code for ...
user444's user avatar
  • 2,126
1 vote
2 answers
271 views

Solving numerical equation with FindRoot with high precision

I try to solve numerically an algebraic equation wich contains Dawson's function. Solutions x of this equation depend on the two parameters a and b. Then I try to plot x versus a for a given b. Here ...
Gallagher's user avatar
  • 713
0 votes
0 answers
69 views

Initial conditions making trouble with NDSolve

I want to solve a number of differential equations in a single NDSolve. The code is as follows: ...
Julian Yussef's user avatar
2 votes
2 answers
108 views

How to remove unwanted branch from a ContourPlot3D?

I have the following Mathematica code: ...
codebpr's user avatar
  • 1,843
0 votes
1 answer
50 views

Algebraic solution of an equation containing an error function

Convolution of a Gaussian with an exponential function (EMG) produces an asymmetric Gaussian, which I want to use for fitting experimental peak data. I am interested in finding an algebraic solution ...
AChem's user avatar
  • 123
2 votes
1 answer
179 views

How to solve abstract functional equations?

Question: If the function f[x] defined on x > 0 is a monotone function, and f[f[x] + Log[1/2, x]] == 3 for any x of x > 0, what is the value of x when f[x] == 0? Cannot be resolved using the ...
csn899's user avatar
  • 3,605
2 votes
1 answer
51 views

Issues finding the minimum of a function over an implicit domain

i am new to mathematica and am really having some problems when finding the minimum of a function over a implicitly defined domain. This is my code: ...
Charlie Mahon's user avatar
2 votes
1 answer
126 views

Consumer Maximization Problem Doesn't Work in Wolfram Mathematica

I'm trying to solve a problem that can be seen in the paper "The Role of the Structural Transformation in Aggregate Productivity". The problem is: Manually it is difficult to find the ...
mjr's user avatar
  • 21
2 votes
1 answer
142 views

Solve taking infinite time

I have a system of equations that should determine the real coefficients {b[1], c[1], d[1],, e[1], f[1], g[1], h[1], a[1], b[2], c[2], d[2], e[2], f[2], g[2], h[2]}....
Slayer147's user avatar
  • 227
2 votes
2 answers
134 views

Quadratic solution is incorrect when quadratic terms is zero [duplicate]

Consider the following input: Solve[a x^2 + b x + c == 0, x] %/.{a->0} The solution produced by Mathematica in the first line is the result of the standard ...
Ubiquitous's user avatar
3 votes
1 answer
67 views

How can I improve the accuracy of FindRoot for a complex equation?

I want to solve the following problem: Given a complex matrix $m=\textbf{m}(λ, ω)$, with $λ, ω \in \mathbb R$, find $λ$ and $ω$ such that $$\det[\textbf{m} (λ, ω)] = 0$$ Since one can take the real ...
fritess's user avatar
  • 33
2 votes
1 answer
104 views

NDSolve: how to solve "ndnum error"

I have a problem of finding the shape of a current. please see the details here NDSolve does not accept the boundary condition I wrote a code but it gives the "ndnum" error. I tested the ...
AWer's user avatar
  • 35
0 votes
1 answer
73 views

Why is Solve unable to solve the given equation?

Here is my Mathematica code: ...
codebpr's user avatar
  • 1,843
1 vote
1 answer
95 views

Unable to simplify complex expression [closed]

I am very new to Mathematica. Somehow Mathematica doesn't give me the norm expression, instead, it just gives the original expression. How should I fix this? The code is: ...
Zhanning Liu's user avatar
4 votes
1 answer
306 views

How many real solutions does $a^{a^{a^x}}=b^{b^{b^x}}$ have?

Let b > a && a > 1, then the equation a^x==b^x has the unique real solution ...
user64494's user avatar
  • 25.7k
0 votes
1 answer
46 views

2D Scalar plot of roots as function of parameters

Suppose I have a function of x with two parameters a,b : f(x;a,b). I want to plot x'(a,b) where x' is the root of the above function .i.e f(x';a,b). I know that for all a and b, the roots real. How ...
NavStoke's user avatar
1 vote
1 answer
57 views

Get limits of values from inequalites

My code above as below; ...
Soon's user avatar
  • 614
0 votes
1 answer
78 views

Matrix equations in mathematica

I need to solve a matrix equation such as $A=S^{-1}A~S$ for a given matrix A. Suppose that the matrices are $3*3$ and A is diagonal. ...
Arian's user avatar
  • 161
6 votes
3 answers
457 views

Projecting the stationary points of a function below its 3D Plot

I have the following Mathematica code: ...
codebpr's user avatar
  • 1,843
2 votes
1 answer
91 views

Manipulate Plot with Find Root Parameter

I would like to plot the function G(r; x') as a function of r, but with parameter x'. x' is the solution to F(x';p) = 0 where p is a parameter I can control. Unfortunately F is messy and I must use ...
NavStoke's user avatar
0 votes
0 answers
49 views

Recursion limit for NDSolve

I have a fairly complex equation containing many terms, I can use the NDSolve for solving the differential equation for lesser terms (6400ish). But can't do it for ...
Bravyi's user avatar
  • 21
0 votes
1 answer
45 views

How to find the Eigenvalues for complicated Bessel boundary value problem?

I am trying to find energy eigenvalues in a problem. A function depends on the radius R (of a quantum dot) and the energy. The function was obtained from matching wavefunctions at the boundary of the ...
Rainforest Frog's user avatar
1 vote
1 answer
66 views

Using ParametricNDSolve does not work for certain parameters

I want to solve the following second-order DE $$ \ddot{w}(t) H(w(t))+\frac{1}{2}(\dot{w}(t))^2 H'(w(t))+g(w(t))(c_0 (\overline t-\underline t)-w(t)) =0, $$ with boundary conditions $\dot{w}(\overline ...
Jerome P.'s user avatar
5 votes
1 answer
78 views

Saving solutions of equations with indexed variables to a table

I am trying to solve a set of equations which are very ugly and have indexed variables. I have a vector of expressions ...
QFTheorist's user avatar
1 vote
2 answers
111 views

How to impose a change of variable in a differential equation?

I have this differential equation in terms of the variable $y$ deq[y_]=y^2 U''[y] + (a y^2 + b y + c) U'[y] + (d y + f) U[y]=0 and I want to make the change of ...
PhysFan's user avatar
  • 63
3 votes
3 answers
113 views

Using FindRoot to solve for coefficient of LinearModelFit

I filmed a small object falling and have data representing its height (in feet) with respect to the frame of the recording. A sample of the data is: ...
GregH's user avatar
  • 1,817
0 votes
1 answer
45 views

Mathematica does not solve all the variable in linear solve. Why?

The below coding contains 9 equations and 9 unknowns. But I have errors every time like "Solve::svars: Equations may not give solutions for all "solve" variables." Does not seem ...
ayyappan jayaraman's user avatar
3 votes
2 answers
203 views

Can Mathematica simplify an ordinary differential equation (ODE) by assuming a power series solution and obtain the recurrence relation?

I have an ordinary differential equation and want to solve it using power series as ψ[x_] = Sum[Subscript[a, n] x^n, {n, 0, ∞}] to obtain the recurrence relation ...
PhysFan's user avatar
  • 63
0 votes
1 answer
81 views

Is it possible to get rid of `Root` and have an explicit closed-form solution for the given equation?

I want to solve the given equation for m>0 where all parameters are Reals and a<0. ...
PhysFan's user avatar
  • 63
1 vote
2 answers
63 views

Numerical search of two simultaneous equations for three unknowns

Given the following two equations with three unknowns $\eta_1, \eta_2$ and $\tau$: $\frac{i e^{-i \phi/2}}{\sqrt{2}} = \cos(2 \tau - \eta_1 -\eta_2)\cos(\eta_1-\eta_2) - i\sin(2 \tau - \eta_1-\eta_2)\...
John Doe's user avatar
  • 329
0 votes
0 answers
43 views

Removing a set of original assumptions from the result of Reduce

I am having trouble using set operations when applying them to lists which cme from the Reduce function. As an example, here is a list of assumptions and an expression for which I would like to know ...
sg1234's user avatar
  • 289
0 votes
1 answer
42 views

Reduction/Elimination of some terms in DSolve output

I have a specific problem regarding differential equation output: As you may see, the first input is my function. ...
Krzysztof's user avatar
0 votes
2 answers
54 views

Solve[] does not return the solution to an easy system of equations [duplicate]

I'm trying to solve the following system of equations: gl1 = b == a - 1; gl2 = b == 3; Solve[{gl1, gl2}, {a}] The solution set provided by Mathematica is empty {} -...
Jan E. Fromm's user avatar
2 votes
2 answers
269 views

How to solve the integral equation?

I have a integral equation like following: ...
yode's user avatar
  • 26.5k
2 votes
0 answers
210 views

Solving `Integrate` of `InterpolatingFunction` from an `NDSolve`

I am interested in solving a system of Differential Equations, particularly u''[\[Tau]]=-f[t]u[\[Tau]] This system has for initial conditions $u(0)=1/\sqrt{2\cdot ...
Jules Alvarez's user avatar
5 votes
5 answers
448 views

How can I select element of a list containing (a,b) where both a and b ara rational numbers and not integers?

I have a list of equations and I solve them ...
Thuy Nguyen's user avatar
1 vote
1 answer
85 views

How to mark the corresponding time points when the switching function changes its value?

q[t] is a switching function, and when Mod [t, \ [Tau]=(2/3) \ [Tau] q[t] changes from 1 to ...
chen chen's user avatar
  • 165
2 votes
2 answers
206 views

Find function by solving equations and imposing constraints

Suppose there are two equations: $$2f(x)+x^2g(x)=8 \tag{1},$$ $$ x^3f(x)+6g(x)=18 \tag{2}.$$ I need to solve these two equations and find the functions $f(x)$ and $g(x)$ in terms of $x$ and constants. ...
Pabitra Tripathy's user avatar
0 votes
0 answers
47 views

Checking Positivity

This is my matrix: H = {{2*a1*p4, -p5*a2, p3*a1, 0},{-p5*a2, 2*a2*w1, -p2, -p1},{p3*a1, -p2, 2*a3*w2, 0},{0, -p1*a4, 0, 2*a4*w3}} Where a1,a2,a3,a4 are non-...
SHR's user avatar
  • 1
0 votes
1 answer
84 views

Finding the solution for the cubic formula over NonNegativeReals

The standard cubic polynomial is: $ax^3+bx^2+cx + d$. And when I used my function: ...
Teg Louis's user avatar
  • 585
0 votes
1 answer
52 views

Problem related to solving a system of functionals [closed]

Can anyone please help me to solve this system with Mathematica? I don't know which command to use ... Thank you very much! I know it can be done by hand, but I would like to know how to do it with ...
rdpdo's user avatar
  • 9
1 vote
1 answer
222 views

Differential complex equations in cosmological problem

I want to solve a differential equation of second order with complex initial conditions. Despite I have wrote all the code with detail, I am still facing some problems I might want to review here. The ...
Julian Yussef's user avatar
8 votes
3 answers
372 views

Poincaré section of the particle motion near the black hole horizon

I am trying to recreate the Poincaré sections given in Figure 2 of this paper. For this purpose, I use the following two methods: Method1: Using ResourceFunction["ClickPoincarePlot2D"] <...
codebpr's user avatar
  • 1,843
2 votes
1 answer
103 views

Finding roots for an expression with non-elementary function

Is there an approach to solving this for $a$ in either closed-form or numerically? ...
Moo's user avatar
  • 3,136
0 votes
1 answer
37 views

How to factorize high-order polynomials that have only complex roots?

I have polynomials like this: ...
homocomputeris's user avatar
4 votes
3 answers
187 views

Finding a specific value from interpolating function

Suppose I have the given code: usol[t_, x_]:= NDSolveValue[{D[u[t, x], x] == Sin[x], u[t, 0] == 0}, u[t, x], {x, 0, 10}] and I need to find the value of ...
codebpr's user avatar
  • 1,843
0 votes
1 answer
147 views

Plot roots of polynomials with beta distribution [closed]

I am a newbie with Mathematica. I would like to simulate/plot the distribution of the roots of both the polynomials and the derivatives of random polynomials. In particular, I would like plot the ...
user52523's user avatar
  • 101

1
2 3 4 5
130