As of May 31, 2023, we have updated our Code of Conduct.

# Questions tagged [equation-solving]

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

892 questions with no upvoted or accepted answers
Filter by
Sorted by
Tagged with
196 views

### Reduce[Sin[x]==0,x] splitting odd and even multiples of Pi

as from Title, I'm wondering why Mathematica does not automatically give a single, simple solution for the problem Reduce[Sin[x] == 0, x] for which I obtain the ...
121 views

### Eliminate variable with partially documented Solve feature Solve[eqns,vars,elims]. Robust?

The Eliminating Variables section on Manipulating Equations and Inequalities documentation quotes an otherwise undocumented feature for Solve ...
275 views

### Spurious DSolve Solution

Bug introduced in 8.0.4 or earlier, persisting through 13.2. DSolve quickly returns solutions to the following PDE (which is the homogeneous portion of the PDE in ...
2k views

### Does NSolve find all solutions?

Is the solution set returned by NSolve usually complete? Can I assume that there are no more solutions than what it returns? Consider systems of equations e.g. ...
264 views

### Strange behaviour of NotElement in Reduce

Bug introduced in 8.0 or earlier and fixed in 11.0.0. Confirmed, as bug, by WRI: [CASE:3527549] I have observed curious behaviour on domains supplied to NotElement...
3k views

### Solve huge symbolic system of linear equations

I have a system of 76 symbolic linear equations (i.e. some coefficients are symbolic) with a sparse coefficient matrix. However, neither Solve[] nor ...
149 views

### Solving a matrix pencil (quadratic eigenvalue) problem with Mathematica

According to Wikipedia The matrix pencil of degree $\ell$ is the matrix-valued function defined on the complex numbers $L(k) = \sum_{i=0}^{\ell} k^{i} A_{i}$. Here $A_{\ell}$ are non-zero $n\times n$...
254 views

### Finding periodic cycles of a function

Given a function f[{x,y}] it is rather simple to use, for example, NSolve to find periodic points of period $n$. We simply take ...
56 views

### Limitations in using Reduce for Integer systems

The System For example, when solving the following system using Reduce in Integers: ...
98 views

### When does Root have a third argument

In Mathematica "11.0.1 for Microsoft Windows (64-bit) (September 20, 2016)", Root[#^4 + 1 &, 2]; actually has three arguments, as can be seen from ...
388 views

I am having difficulties implementing a Neumann value when numerically solving the Navier equation using NDEigensystem. The Navier equation is given by $\nabla^2 \vec u + (p^2 - 1) \nabla(\nabla\... 4 votes 0 answers 467 views ### Extending Bresenham's algorithm for subpixel rendering Original Bresenham's line drawing algorithm it limited to drawing lines between two integer pixel positions and does not allow subpixel rendering. However with my reformulation of this algorithm as a ... 4 votes 0 answers 371 views ### Stability analysis of transcendental equation (stability crossing curves) I am working with a non-linear delay system with three scalar delays. After taking the Laplace transform of the linearized system, the characteristic function is a transcendental equation with three ... 4 votes 0 answers 329 views ### Solving Thue equations A Thue equation is a 2-variable homogeneous integer polynomial of degree at least 3. It's well-known that such equations have only finitely many solutions over the integers. I'm trying to solve some ... 4 votes 0 answers 419 views ### Am I entering this 2-variable recurrence correctly? I'm trying to solve this recurrence with two variables. RSolve[g[d, n] == 1 + g[d - 1, n] + g[d - 1, n - 1] && g[d, 0] == g[0, n] == 0, g[d, n], {d, n}] ... 4 votes 0 answers 176 views ### Symbolic solution to ODE, pure InverseFunction not evaluated I'm new to Mathematica and I don't understand why in the solution of the following ODE, the #1 in the pure function is not immediately replaced by the corresponding ... 3 votes 0 answers 63 views ### Can I use FindInstance to prove an algebraic identity? This question arose from a [now removed] MathOverflow discussion, where a Null result from a FindInstance query was used to prove that$f(x_1,x_2,\ldots x_n)\neq 0$has no solution in$\mathbb{R}$. My ... 3 votes 0 answers 81 views ### Simplifying formula for a real-valued root of the quartic I have a minimization problem which reduces a 4th degree polynomial with a real valued root. It's easy to get explicit formula for this root, but formula involves imaginary parts which always cancel ... 3 votes 0 answers 38 views ### Numerically solve a non-differential equation with InterpolatingFunction as output I have some a function that I need to solve numerically over an entire domain (Ideally I would like an InterpolatingFunction object as output), which does not include any derivatives. I have found a ... 3 votes 0 answers 80 views ### How to improve this code? The aim of my work is to find a value for the complex constant$\omega$. In order to do that I solve the below system of differential equations with a manual shooting method: I first solve the system ... 3 votes 0 answers 65 views ### Different output to Solve command in Mathematica changing a variable for a subscripted variable I have a system of equations that is solved with the Solve command in Mathematica 10.2, when one of the variables is changed for a subscripted variable the answer is not the same, the difference is ... 3 votes 0 answers 257 views ### Errors Using FindFit and FindRoot I'm trying to fit the following equation to data: where and x and y are the dimensionless variables x=V/Vr and y=Ir/(2*I0). n=1 and I'm trying to find Vr and R. The blue is an example of the curve ... 3 votes 0 answers 152 views ### Unexpected Behavior of Parametric Sensitivity in ParametricNDSolveValue Bug introduced in 10.4 or earlier and continuing through 11.3 Submitted as CASE:3916971 While exploring alternative methods of solving 33538, I encountered difficulties with the parametric ... 3 votes 0 answers 136 views ### Solving Monster Equations with Mathematica I would like to solve the following equations in Mathematica. Here are the formulas:$u=0.5\alpha=0.5\epsilon_0=0.1\epsilon_1=0.1f_0(y)=\mbox{Gaussian density with mean -1 and ...
Suppose that one wants to calculate the surface charge density of a polarized dielectric ellipsoid, prolate ellipsoid with long and short axes as $a$ and $c$ where $a$ is parallel to the $z$ axis. $a$ ...