# Tagged Questions

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

0answers
33 views

### why is NSolve giving {y,x} in place of {x,y}? [duplicate]

Why is NSolve giving an inverse set of solution? Is it a problem with my computer only? ...
1answer
167 views

### How to Solve[] for rational constants?

I am trying to solve a system equations for rational, constant coefficients: ...
1answer
82 views

### Find a minimum value which satisfies an equation

I have to find a minimum value of "a" which makes x=-a+b+c, y=-a+b+c^2 positive where a>1, 0 ...
1answer
109 views

### Inaccurate answer for a system of equations

When I solve the following system of 6 equations by NSolve, it gives me an answer set; however this answer won't make the 2nd equation equal to zero (i.e. when I put the answers into ...
3answers
199 views

### How to find the solutions to $a+b+c+d=60$?

How can I find all the solutions to: $$a+b+c+d=60\quad (0\leq a,b,c,d\leq 30,\; a,b,c,d\in\mathbb N)$$ I've tried to use Solve[], but it says that there are more ...
2answers
103 views

### Solving two variable using two expressions each involving summation

I am trying to solve for h1 and h2 using function solve as in below code, Expression in solve has two equation each equates sum ...
1answer
73 views

### Complex Polynomial roots [closed]

I have the polynomial $p(z)=1-z^3$, I am using mathematica to get all three roots of $p$, say $a, b$ and $c$, obviously $$1-z^3=(z-a)(z-b)(z-c)$$ However, mathematica gives a wrong answer by saying ...
2answers
75 views

### Getting the first solution instance

How do I get Mathematica to stop a solver and give a result as soon as it finds the first solution instance? I tried this: ...
1answer
64 views

### Solve not returning anything

I have the following function: ...
0answers
54 views

### Sharp Ratio Maximization, Closed Forms

I am trying to get a closed form for the following first order conditions (n=4): Here's the nb-File. The code is as follows: ...
1answer
56 views

### Trouble in finding instances of values of variables that satisfy an inequality

Consider the following mathematical expression with complex numbers (phasor) and two variables (lambda and ia2): ...
1answer
250 views

### Solving $\frac{dx}{dt} = A \frac{ (1-x)}{(t-t^2)} - \frac{(B*x -C*x^2)}{(t-t^2 )*(t-x)}$

I would like to solve the following equation: $\frac{dx}{dt} = A \frac{ (1-x)}{(t-t^2)} - \frac{(B*x -C*x^2)}{(t-t^2 )*(t-x)}$ I have already posted it here, but still it doesn't work for me (I don'...
1answer
125 views

### Closed form of two-layer recurrence

I am trying to find a closed-form expression for $A(0)$, described by the following recurrence forms, as a function of $L$ and $d$: \begin{align} A(\ell) &= 1 + 2^d A(\ell+1) + \sum_{g=0}^{d-1} \...
1answer
151 views

### Plotting level curves for 2-variable exponential equation (Lotka-Volterra) - how?

I have $$\frac{e^{(d x + b y)}}{x^c y^a}$$ Incidentally, this is the energy integral for Lotka-Volterra as given by my lecturer's notes. I would like to draw the level curves for this equation for ...
0answers
74 views

### How much time for solving a system of equations?

I wrote the following code for system of 11 equations; however when I run, it shows "Running" and has not converged to any answer after 2 hours. Please let me know whether it is normal or how I should ...
1answer
79 views

### Problem in solving non linear set of equation?

I am trying to solve a set of non linear equation but using the function nsolve but mathematica is not giving me proper answer. The code is given below. ...
2answers
189 views

### Exporting and Importing solution sets from NSolve

I have a rather large data set that I need to solve for, then save to my hard disk and import in the same format at a later time. This proves to be tricky. I use ...
1answer
97 views

### Solve for a variable using expression involving sum of quantities

I am trying to solve for h1 using function solve as in below code, Expression in solve equates sum of two expression. Both left hand and right hand side of expression is the sum of four quantities ...
2answers
351 views

### DSolve returns a “wrong” solution

This wrong solution exists from mma9 to mma10.1: ...
0answers
38 views

### How to solve a system of equations which includes vectors? [duplicate]

I'm starting to wonder if this is something that mathematica just can't do? I thought something like this might work: ...
2answers
330 views

### Solving a two variable two equation trig expression

I am trying to use Solve to get what two angles (A and B) are in a problem I have. ...
1answer
64 views

### Reducing a system of vector equations

I'm trying to solve a system of vector equations. I know this is solvable since I've done it myself by hand (I reduced it to solving the root of a quartic anyway). I'm trying to do it in Mathematica ...
0answers
123 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 ...
2answers
538 views

### Solving an equation takes too long

I am trying to solve the following equation func[a, b, c, d, e] == 0 where ...
1answer
44 views

### Defining a function in terms of a solution returned by Solve

The title is a little ambiguous, but I didn't know how else to put it. What I'm trying to do is solve a system of equations ...
1answer
92 views

### Use FindRoot to get the root with minimum imaginary part

For example, define test[z_] := Cosh[0.5132928614530164 z] + 0.5934823341977118 Sinh[0.5132928614530164 z] And ...
1answer
67 views

### List manipulation performance or how to make independent list copy

I have a task to solve some system of equations with NSolve and print graph of it, depends on parameters. Something like this (maybe it is not a good example and does not always have a solution, but ...
1answer
105 views

3answers
633 views

### Finding intersections of two parametric curves

I am dealing with the root finding of two parametric data curves (data below). I have already checked Parametric Interpolation of 2D data, which I found useful for plotting, though it is not adequate ...
1answer
283 views

### Synchrotron Radiation and ListDensityPlot

I'm trying to reproduce the following plots: As described by this blog entry: Synchrotron radiation As you can see in the linked article, the task is essentially to make a ...
0answers
58 views

### NSolve running for ever

I have troubles running NSolve for my physics problem. I am new to Mathematica, which is why I might be missing some key solutions. I have the following function with the variables: ...
0answers
91 views

### Solution Branch Switching of Quartic

Im using a closed form solution for quartic equation. In the quartic equation, there are parameters that are being varied and therefore the solution changes depending on these parameters. The ...
1answer
118 views

### Solve seems broken after I installed the package Tomatlab.m

After I downloaded the Mathematica package ToMatlab.m, Solve does not work as before: ...
1answer
281 views

### Using a Mathematica index as a DiscreteVariable in NDSolve when solving a coupled set of ordinary differential equations

Context Since the explanation below of the problem to be solved is lengthy, let me preamble this by saying that I have code that works to solve the problem, but I don't know whether (1) it's ...
2answers
56 views

### Selecting the maximum value from the results returned by NSolve

I'm trying to select the maximum value from the answers Mathematica 7.0 is getting from a simple basic NSolve algebric equation : ...
3answers
318 views

### Solve: Merging two branches of the solution

I have the following code: ...
1answer
60 views

### using FindRoot to solve 3 simultaneous equations [closed]

I'm trying to solve 3 simultaneous equations derived from an electrical circuit of a common source amplifier. ...
0answers
156 views

### How can I improve the solution of my PDE?

I want to improve the last code to find a better solution for umi. For now I'm using only MaxStepFraction. Also, when I put no ...
1answer
97 views

### A question about calculus and Programming

I am a very new user and I would like to know how to calculate the following operations in Mathematica. Honestly this is not a homework. I am an french architect and I would like to be back in Math ...
1answer
79 views

### Sign of a symbolic expression as a function of parameter values

I need to know the sign of the following expression for p[t] = z/(1-a), as a function of the parameters {a, b, c, z}: ...
1answer
141 views

0answers
82 views

### How to determine why Solve[] failed?

I don't know what to make of Solve[] failing on this: ...
1answer
120 views

### How to speed or help Solve[] when it is stuck?

The code below generates a system of equations that I need to Solve[] for {c[5], c[6], c[7], c[8]} in terms of {c[1], c[2], c[3], c[4]}. ...