# 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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### Manipulate parametters inside NSolve with complex variable

I think my question should be simple but I couldn't figure out a nice way to do it. I want to find zeros of a complex function (variable $z$) with real parameters ($\nu$, $\alpha$, $\xi$). My goal is ...
1answer
59 views

### FindRoot not obtaining solution for nonlinear system of log equations

There is a system of 9 non-linear equations, eq containing logarithms that I think it should be solvable numerically. There are a total of 9 variables with two of ...
1answer
46 views

### How to refer a solve answer to NDsolve [closed]

I don't know how to refer a solution of Solve to compute it in NDSolve, here's my code ...
1answer
30 views

### Read the graphic at another value

So I got this code and I'm new at coding, what I want to do is just read the graphic at a value of the Y axis and get the value of the X axis ...
2answers
59 views

### Obtaining the other axis value

I'm new at coding and I got this simple differential equiation and the plot of this function involved, I can obtain the value of the dependant variable based on the independant varible as usual, what ...
1answer
235 views

1answer
52 views

### How can I find in Mathematica if my equation have solution or not on a given interval?

I'm new to Mathematica. I usually used Wolfram Alpha; however, since the equation that I'm working with is a long equation I need to use Mathematica. This is an example of the problem. So, I want to ...
0answers
45 views

### Instability (quasi-randomness?) of results given by NDSolve [closed]

I am running on Mathematica 11.3 an unfortunately long NDSolve for Pontryagin principle (SIR epidemics), with both initial and ...
1answer
77 views

### NSolve for system of 14 non-linear equations

I am really new to Mathematica. Trying to solve the following system of equations (below). Get an error from Mathematica and have no idea what is the problem. Will very much appreciate any help. ...
1answer
45 views

### Solve error in multivariable equation

I have the code that works for one variable equation. However, when I modify it to include two coupled equations, solve gives me the error message which I do not understand. Below is the working code ...
0answers
55 views

### Solving partial differential equation

I am new to mathematica and I want to solve the following pde. I have two boundary conditions and one initial condition. I have tried the following code but the output is not the solution and it's ...
0answers
38 views

### NMinimize subject to many complicated conditions not obbeying imposed equation

This question derives from (and refers to) this one asked by me, and I hope that creating a new question rather than editing that one is appropriate. There I ask for a way to find the subset of the ...
1answer
70 views

### Does anyone here know how can we extract Lambda from the following equation

I am working on an estimation problem where I have the following Code is A = 1 + Pi*Csc[(1 + Pi)*\[Lambda]]^2* (Pi + Sin[2*(1 + Pi)*\[Lambda]]) Can anyone ...
1answer
74 views

### Why is my plot empty? [closed]

I'm trying to plot a PDE solution with this code: ...