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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0answers
45 views

Multiple layered FindMinimum

I have a function SQ[b, zQ, zh] where I can find at which zQ it is a minimum, b=0.1 and <...
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2answers
104 views

Integration NSolve problems

I have some problems in solving this equation numerically in Mathematica. Mathematica gives me the error message "NSolve::nsmet: This system cannot be solved with the methods available to NSolve&...
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31 views

How can I set the plot range to the point where the function becomes zero?

I have a lot of functions (mostly exponential included and more precisely complicated combinations of Gaussian and Slater ones) which decay and become zero in the different points depending on the ...
4
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1answer
126 views

Calculate median of pdf using NSolve [closed]

I was trying to compute the median of a pdf using NSolve, defined such that $$ \int_{0}^{\rm median}p(x)dx = \frac{1}{2} $$ but NSolve seems unhappy about solving for an upper limit of an integral. A ...
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40 views
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1answer
76 views

How to format linear equation solve

I need to solve the system of linear equations $S_i = \sum_ {r = 1}^\lambda x_ {r, i} E_r$, where $S_i$ is a $\lambda$ - dimensional vector, $i$ runs from 1 to $n$, $r$ runs from 1 to $\lambda$,...
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1answer
58 views

Solve cannot return NOT[A==B] in equations results

can you help me to return NOT[A==B] for Solve operation. in below code it does not return zP!=14 ...
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1answer
38 views

How to remove the domain of variables in result relation?

this is my relation and it returns me xP [Element] Integers. I do not want any kind of these information. for example, I just need to see for every relation, yp-> x+1 - xp , thanks ...
-1
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2answers
155 views

How to plot this implicit function? [closed]

The command ContourPlot[{RealAbs[x + 1/y] + RealAbs[10/3 - x + y] == 10/3 + y + 1/y}, {x, -5, 5}, {y, -5, 5}, PlotPoints -> 50] , as one sees, draws ...
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1answer
43 views

Get Real Solutions works in Solve but PositiveReals don't (Quantities)

I'm trying to get the R+ Solutions to a school problem with solve. Everything works fine with Dom -> Reals but when I try ...
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1answer
75 views

Solve a differential system of equations in time

I am trying to solve a system of 3 equations and 3 unknown variables that change in time (Tw(t), Tcor(t), Texit(t)). ...
2
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1answer
88 views

Why does Solve produce a result in terms of one variable, but not the other?

I have the following quartic equation:\begin{equation} x^4 + ax^3 + bx^2 + ax + 1 = 0 \end{equation} and I'm trying to find relations for $a$ and $b$ for which we have multiple roots. To this end, I ...
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1answer
60 views

How to get a single solution by simultaneously solving three equations with three variables? [closed]

I'm trying to solve the following three equations having three variables. ...
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0answers
51 views

NDSolver cannot give precise result for extremely small values

I would like to solve an ODE with MMA. The equation is simply the Coulomb law. However, I cannot get a satisfying result: ...
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1answer
79 views

How can transform the question into Wolfram language? [closed]

I've been sitting with this question: A graph has 7 corners. The degree of each corner of the graph is 3 or 4. How many edges does the graph contain if both degrees are represented? And this is the ...
2
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0answers
48 views

Defining new Domain for variables

I am trying to define a new Domain for variables to use with functions like FindInstance or Solve. For example, If I wanted to solve x+y+z=1 over the Reals, I'd get a large solution space. But If I ...
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1answer
65 views

Trying to solve a basic Lagrangian optimisation problem

New to Mathematica, trying to solve a simple economics problem but having troubles with using Solve and Eliminate. The question: Now suppose that this agent makes two choices, expressed by x and y ...
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1answer
111 views

How to solve \[Theta]23 from the following equation?

How do I solve [Theta]23 from the following equation? ...
2
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3answers
141 views

Solving implicitly a trigonometric equation

I am trying to solve this equation with respect to L: L== ((9.81*T^2)/(2*Pi)) Tan[2Pi*d/L] Since you have the unknown ...
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2answers
84 views

Assigning A Symbol To A Second DSolve Solution

I am looking for a way to compress a lengthy DSolve solution to a single symbol, kind of like assigning a variable. I have this expression: ...
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2answers
71 views

how to get the result without conditional expressions

I am working with JAVA API and send a relation to kernel, then receive the returned solved result. Although I explicitly mentioned in my relation to have Integer Elements, the returned expressions ...
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1answer
37 views

How to solve two IntegerPart function in Reduce?

Here I have two Functions, which involve IntegerPart. For example: f[x_] := IntegerPart[-0.002*x*(x - 1000)] q[x_] := IntegerPart[-0.002*x*(x - 2000)] Then I want ...
2
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2answers
111 views

Find relationship between parameters to prove conditions of eigenvalues

I have the following 3-by-3 matrix. I need to find condition(s) on the parameters 'a' and 'b' such that this matrix has exactly 1 eigenvalue bigger than 1 in absolute value and other two eigenvalues ...
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2answers
147 views
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0answers
70 views

Can mathematica numerically solve this system of coupled integro differential equations?

Here's my system: R(x,y,t) is the concentration of a chemical that's diffusing across the box. The disk is a mobile sink for the chemical, which absorbs it in proportion to its concentration. The ...
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0answers
39 views

Introducing FindRoot in a ReccurrenceTable but problem with the starting point

I would like to introducing FindRoot in a RecurrenceTable, that uses the previous result as a starting point. My equations are defined as following: ...
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2answers
81 views

How to find a matrix satisfying following equation

I have a $N \times 1$ vector $F(t)$ for $0\leq t \leq 1$. I want to find a $N\times N$ Matrix $C$ (a real-valued matrix) satisfying the following equation: $$\int_0^t F(t_0)dt_0= C.F(t)$$ If it ...
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3answers
161 views

How do I improve this code for hyperbolic numbers so to allow equation-solving?

I have the following code, which allows evaluating expressions with split-complex unity J: ...
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0answers
54 views

Is it possible that NSolve gives the roots that the function is not (well-)defined at those points? (an example is given)

I have this function for reals values of $x$ for $2<x<3$. $$f(x)=(3 \pi -2 x)^2 \sin \left(\frac{1}{2} \left(\csc ^{-1}\left(\frac{4 \pi (\pi -x) \csc \left(\frac{\pi ^2}{\pi -x}\right)}{4 x^2-...
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2answers
55 views

SolveValues function gives weird output

On Sep 21 edition of Notice of the AMS, it describes a few problems the mathematicians are working on, one of which reads: $x^3+y^3+z^3=n$ for which integer $0<n<100$; are there solutions with $...
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0answers
97 views

Solving two transcendental equations

I have real and imaginary parts of a characteristic equation as follows: ...
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1answer
90 views

Is there any alternative for NSolve or Solve to obtain all the roots of the given function?

I have this function for reals $0<x<\pi$. $$f(x)=(3 \pi -2 x)^2 \sin \left(\frac{1}{2} \left(\csc ^{-1}\left(\frac{4 \pi (\pi -x) \csc \left(\frac{\pi ^2}{\pi -x}\right)}{4 x^2-8 \pi x+5 \pi ^...
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0answers
40 views

How can I make sure if the given function has any roots which are not rational multiples of $\pi$?

I have this function for $0<x<\pi$. $$f(x)=(3 \pi -2 x)^2 \sin \left(\frac{1}{2} \left(\csc ^{-1}\left(\frac{4 \pi (\pi -x) \csc \left(\frac{\pi ^2}{\pi -x}\right)}{4 x^2-8 \pi x+5 \pi ^2}\...
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1answer
107 views

Equation solving with magnitude constraints incredibly slow

Somewhat complicated question and sorry in advance if it is presented poorly. I'm running Mathematica 12.0 (haven't updated to 12.1 yet). I'm trying to solve a set of linear complex equations with ...
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2answers
87 views

How to "read" the solution of an inequality?

The solution of fun[x,y]>0 leads to the following output ...
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2answers
89 views

NSolve unable to solve system of equations with domain specification

I have a system of two equations in two unknowns that I would like to solve with NSolve within a specified region. However, while Mathematica solves the system if I omit the domain specification, it ...
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1answer
62 views

How to calculate multiple solutions from big to small with FindInstance funtion

I want to find the nearest 50(or 80, even 100)solutions under 1.4628 from big to small, I tried FindInstance function in MMA, but still cannot get the desired results I need.Here is my code: ...
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0answers
90 views

Solving set of equations with complex variables (looking for critical points)

I need to solve (a more complicated version of) the following set of equations : ...
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1answer
63 views

Simplify an expression with assumptions connected with OR

Mathematica doesn't seem to have any problem with these commands: ...
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1answer
110 views

Solve for p of Binomial distribution

Is there a way to solve for the probability p of a binomial distribution in a set of equations? With some arbitrary functions g[ _ ] and f[ _ ] such that: ...
2
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2answers
137 views

How to get multiple solutions ranked in order?

I want to get 10 solutions nearest to 100, however the following code returns too small answers, how can I realize my thought? ...
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0answers
83 views

Different solutions for an equation

I have a problem with Mathematica, When I solve this equation in Mathematica and also in wolframalpha I have different solutions [[1] ...
13
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3answers
554 views

Routh-Hurwitz criterion not giving correct answer when done manually?

Consider the system: \begin{align} \frac{dS}{dt} &= \nu N -\frac{\beta S I}{N} + \xi R - \nu S\\ \frac{dE}{dt} &= \frac{\beta S I}{N}- \sigma E -\nu E \\[2ex] ...
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1answer
89 views

How to replace either one of the variables?

Here's my code: ...
2
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0answers
97 views

Solving a complicated, non-polynomial dispersion relation

I am quite new to Mathematica, so I apologise if the following question is very basic; I can't seem to find an appropriate answer anywhere! I am trying to solve a quite complicated dispersion relation ...
3
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2answers
250 views

How to visualize a Lagrange problem with Mathematica?

I had asked a question here, which I was advised to open a new question for my further problems. I have a function as $f(a_1, a_2) = a_1^2 \sigma_1^2 + a_2^2 \sigma_2^2$, which is subjected to the ...
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1answer
82 views

Is there any possibility to visually examine a Lagrange problem with Mathematica?

I have the function: $f(a_1, a_2) = a_1^2 \sigma_1^2 + a_2^2 \sigma_2^2$, which is subjected to the constraint: $a_1 + a_2 = 1$. I have obtained that: $$a_i = \frac{\sigma_i^{-2}}{\sum_{j = 1}^2 \...
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1answer
92 views

Rewrite a variable in terms of another variable

I have two variables t = 1/Sqrt[2] (Sqrt[1 + Cos[a]] + Sqrt[1 - Cos[a]] + Sqrt[1 + Cos[b]] + Sqrt[1 - Cos[b]] + Sqrt[1 + Cos[c]] + Sqrt[1 - Cos[c]]) and <...
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0answers
101 views

Axes ticks scaled in powers of ten

I'm trying to plot the solution of an ODE and I would like to have the ticks in powers of ten. Although, this happes automatically from Mathematica for small orders, such as ...
6
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2answers
775 views

Why does Mathematica not give the simple solution of the given equations?

I want to solve this system of two equations for $x$ $$\{ \sin (2\pi x)+\sin (\frac{2\pi}y)=0 \quad , \quad \cos (2\pi x)-\cos (\frac{2\pi}y)=0 \} \qquad (1)$$ I use ...