Tagged Questions

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

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1
vote
1answer
61 views

handling division by zeros and line equations

today I was writing a code which takes some line equation and a circle equation,finds intersection points that are on $II$ and $III$ quadrants,draw a tangent line to circle from that point and then ...
1
vote
1answer
26 views

problem on returning value of function as a list using if

today i was writing a function for my project using mathematica that gives a line equation in form of $y=mx+b$ and a circle equation in form of $x^2+y^2=r^2$ and finds the intersection point which is ...
0
votes
2answers
62 views

How to solve ArcSinh equation for many differents parameters?

I am totally stuck trying to solve the equation below (1/2) x Sqrt[1 + 4 a^2 x^2] + ArcSinh[2 a x]/(4 a) == d Where a and ...
0
votes
3answers
59 views

High-Precision NSolve

I need to calculate the intersection of two curves f1[x_] := ((Zl ρ ) Exp[-x]) f2[x_] := (α k e^2 /x^2) Where ...
0
votes
0answers
38 views

Problem with solving an equation [duplicate]

I dont understand why Mathematica cannot solve this equation: Solve[Log[x^2 + 5] + 0.5 x + 1 == 0, x] I get this error message: Solve::inex: Solve was unable to solve the system with inexact ...
1
vote
1answer
99 views

Solving systems of equations

So I have a set of equations like 12 of them but 13 variables. However I would like to find the numerical value of the roots for the maximum value of a particular variable. I don't know how to do that ...
-2
votes
0answers
37 views

How dose solve this equation for a group of x,y, slope of shape [on hold]

This is equation of an ellipse. 5*Y-12*ARCTAN(7*Y/X^2+Y^2-(3.5)^2)=0 OR TAN(5*Y/12)-7*Y/[X^2+Y^2-(3.5)^2] how solve this equation for a group of x,y? (Discretization of shape) How to solve for ...
2
votes
4answers
316 views

Solving puzzles with Mathematica

I would like to be able to solve logic puzzles such as the one described here using Mathematica. I have copied & pasted the listed example below to save on jumping about with hyperlinks: The ...
0
votes
1answer
44 views
0
votes
1answer
30 views

Manipulate Solve for initial condition

I have a series of $n$ coefficients with parameters $r$ and $b$ that sum up to one. But there i also the initial condition value $c1$ that i required to obtain this normalization. I want to find this ...
0
votes
0answers
42 views

Closed solutions for `FindRoot`, no solutions for `Reduce` or `Solve` [duplicate]

Reduce, Solve and FindRoot all appear to struggle with this: ...
0
votes
0answers
56 views

Using NMinimize to solve the Multi Commodity Flow problem

I have the following optimization problem and I was hoping to solve it with NMinimize. Unfortunately, I don't get the desired result. I would like to get an optimal vector for $d_{e}$. This is how ...
1
vote
1answer
42 views

How do I solve a profile interval (statistics)

I want to calculate a 95% profile interval for f0. Do worry too much if you do not understand what it is. I will illustrate with a simple example. ...
0
votes
2answers
53 views

Plot function the uses Solve

Can someone tell me why I get an error (and how I get around it) from Solve while I try to Plot a function like: ...
6
votes
3answers
167 views

Ovals of plane curves (and esoteric surfaces in space)

Consider the curve $y^2 - x^3 + x=0$ with $x, y$ real. This curve has two connected components (one bounded, one not), and the question is: how do you get Mathematica to tell you that (if you do: ...
1
vote
2answers
117 views

Solving Differential Algebraic Equations as BVP

I am trying to solve a set of DAEs. \begin{equation} -4 \nu (\lambda(s))^{(-1 - 4 \nu)} \theta'(s) \lambda'(s) + (\lambda(s))^{(-4 \nu)} \theta''(s) = -\alpha_y \cos\theta(s) + \alpha_x ...
0
votes
1answer
40 views

How find solve the equation complex conjugate? [closed]

Tried solving it with every function I know but couldn't z*=z^2
0
votes
0answers
53 views

Solving an equation for rational modulus 1

I want to solve an system of equations of the form $$\prod_{i=1}^n x_i^{M_{i,k}}=1 \qquad k=1,\ldots,n$$ with complex $x_i$ with constraint $|x_i|=1$ and $M_{i,k}$ integers. This is basically a ...
1
vote
3answers
43 views

`Solve` with variables as single vector

Say I have a set of equations where the unknown variables are the elements of a vector $c=(c_1,c_2,\ldots)$ and want to solve it for $c$. Is there a way to do this with ...
2
votes
2answers
117 views

Solving 4 variable system of equations

Trying to solve a systems of equations. Here's the code: ...
1
vote
1answer
54 views

How to calculate minimum positive solution of a equation?

Equations with triangular function usually have multiple solutions, like Solve[Sin[x] == 1/10, x] returns a solution like ...
0
votes
1answer
47 views

How can I stop the integration of NDSolve with a condition?

I try to solve a partial differential equation by NDSolve. At some point, I want to stop the integrating by a condition that compares the min value of the function ...
2
votes
0answers
97 views

What is the algorithm behind Mathematicas Reduce in this equation?

Mathematica can use Reduce to arrive at an answer in this equation ...
2
votes
1answer
137 views

Solving a system of nonlinear equations 2

Regarding this question: Solving a system of nonlinear equations When I try to solve the same system (with the code proposed in Daniel Lichtblau's answer) with different Right Hand Side values, ...
1
vote
1answer
70 views

Matrix elements scope definition

Alright, I'm very new to Mathematica and I have yet to learn a lot so please bear with me (sorry if this is a duplicate!): I want to create an $n\times n$ matrix $C$ with elements $c_{i,j}$ with $i,j ...
5
votes
3answers
177 views

Not able to get a solution to a Lagrange Multiplier Equation

I assigned several constrained optimization problems to my calc IV students to solve with Mathematica, but this one is being stubborn. The function to optimize is: f(x,y,z) = y Exp[x-z] with the ...
2
votes
1answer
88 views

Problems with NDSolve and partial differential equations of several variables

Suppose we have the following partial differential equation: $$ 0 = \frac{ \partial w }{ \partial \tau } + \left( w + \sqrt{ h + \beta } \right) \frac{ \partial h }{ \partial \chi } $$ where $w$ = ...
0
votes
0answers
60 views

Undocumented options for NSolve

There are many undocumented options in Mathematica's official documentation. Is there a tutorial, or a reference somewhere, that explains in detail the undocumented uses of ...
1
vote
0answers
62 views

Numerical solution to two non-linear coupled differential equations [closed]

I am trying to solve two differential equations representing the position of an object in space. I have specified arbitrary initial conditions. ...
1
vote
0answers
40 views

Creating a matrix from a list of simultaneous equations

I have a list of n simultaneous equations of the form, w A[n] = (K[n,n+1]+K[n-1,n])A[n] - K[n,n+1]A[n+1] - K[n-1,n]A[n-1] ...
1
vote
1answer
77 views

Find extreme values in a polynomial expression

I have been hunting down and could not find an answer to my question. As I've now been struggling for quite a while and believe it is a simple trick that's preventing me from getting over this ...
3
votes
2answers
123 views

Solve and Reduce with Log finding unexpected root

We give equations like $\ln(1-x)-\ln(x-2)=0$ to our calculus students. This equation clearly has no solution, since $\ln(1-x)$ is only defined if $x<1$ and $\ln(x-2)$ only if $x>2$. Still, the ...
0
votes
0answers
42 views

Faster way to use Solve in a multiple parameters function

I have a complicated function, G, of several arguments: $G[{\lambda1,\lambda2,a,b,c,d,\sigma u,\sigma v,\rho,q}]$. First, I want to fix a=0.5,b=0.7,c=0.4,d=0.35, q=1. Then, I need to find the values ...
1
vote
1answer
49 views

How do I find the expression for where the first derivative equals 0? [closed]

I have a simple function of time. If I take the first derivative and set it equal to 0.0 I get the extrema of that function. I'm not interested in a numerical result, I want an expresion involving ...
1
vote
1answer
51 views

Export data from NDSolve when they meet a certain condition

I need to export to a txt file the data from the following system of equations: ...
1
vote
1answer
55 views

Getting unwanted solution from Solve

I am solving the simultaneously equations $\quad \quad x_7=0$ and $\quad \quad 6x_4x_5+6x_3x_5x_6+zx_4x_7^2+zx_5x_7^2=0$ with Solve. Here, $z$ is an unknown ...
2
votes
2answers
57 views

what to do when NSolve does not solve

f = 696.1125540355472 + 3.9668099604385043 x + LogGamma[1 + x] - LogGamma[169 + x] Plot[f, {x, 0, 10}] Solve[f == 0, x, Reals] NSolve[f == 0, x] I know that the ...
1
vote
1answer
31 views

Error following a variable in an ODE [closed]

I am trying to solve a 4th order differential equation and this is my code thus far ...
0
votes
0answers
31 views

Boundary condition is not specified on a single edge of the boundary of the computational domain

When I want to solve this PDE I get this error "NDSolve::bcedge: "Boundary condition u[0,0.05]==0 is not specified on a single edge of the boundary of the computational domain"" ...
3
votes
1answer
89 views

Importing data from Matlab, using data in “NSolve” and send the results back to Matlab

I have generated an image processing code in Matlab. It has several subroutines and in one of them, I should solve a system of 7 nonlinear equations. I use "fsolve" in Matlab to solve this system, ...
0
votes
0answers
99 views

Poincare Section of an Hamiltonian

I'm in desire to plot the Poincare Section of a differential equation defined by a hamiltonian system. The hamiltonian is as follow: ...
1
vote
1answer
47 views

Strange functioning of RegionPlot with Reduce's output

I have defined this two quantities: f = (-b + Sqrt[b^2 + 4 a])/(2 a) g = (-b - Sqrt[b^2 + 4 a])/(2 a) and I want to solve this system in function of $a$, for ...
1
vote
2answers
146 views

Eliminating the Parameter: Transform parametric equation to Cartesian equation and draw arrows along parametric growth

Hey guys I really could use some help on this calc 3 problem. I'm stuck on how to write the code for this problem: a) Eliminate the parameter to find a Cartesian equation for a parametric curve. b) ...
-2
votes
1answer
67 views

Solve a system of two equations only in Mathematica [closed]

x + Sinh[x] == Sin[y] + y z + Exp[z] == x + Log[1 + x] + 1 M={0,0,0} x-? y-? z-? Solve[] doesn't solve this system.
0
votes
1answer
88 views

Attempt to solve for Differential Equation - Acc, Vel, Pos in (x,y,z) [closed]

In the problem I'm working on, there is a tennis ball that is subjected to a headwind, tailwind, and crosswind. I am trying to use NDSolve in order solve for the position functions and to eventually ...
0
votes
1answer
50 views

NSolve super slow for a parameter scan

I am using NSolve to solve two equations for two variables while scanning through several values of angles. The strange thing is that when I manual enter a value for the angle and Nsolve the answer is ...
2
votes
2answers
116 views

How can I get Solve to combine Sin/Cos into Tan?

I want to solve an equation in x, containing Sin[x], Cos[x] and a positive real constant ...
1
vote
1answer
94 views

Solving a System/Matrix of Equations in Matrix Form

Ok, I am trying to solve an equation involving matrices (well, tensors actually), which is of the form: $\mathbf{e}^{T} \cdot \mathbf{M} \cdot \mathbf{e}$ = $\mathbf{N}$, where $\mathbf{e}$ is an ...
0
votes
1answer
57 views

Display solution of Solve without the arrow [closed]

Is there a way to format Solve or something that I get the result of a calculation without the arrow, so if my result is like ...
0
votes
1answer
61 views

Solving at zeroes of a matrix - code only works for simple equation

I have a matrix of zeroes (True) and non-zeroes (False). The matrix is generated from a table of values of two other variables. I'm trying to observe how the solution for p3 changes with small ...