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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42 views

Set of multivarible expressions to be re-expressed a single variable

I have a set of expression such as $\frac{3x+y-z}{6x}$ and $\frac{3 x-y+z}{12 x}$, which can easily get re-expressed as $p$ and $(1-p)/2$, where $p=\frac{3x+y-z}{6x}$, but is there a way to find this $...
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2answers
70 views

Solving equation for a parallel capacitor

I am a beginner at Mathematica and am trying to solve a simple equation. There are multiple ways to solve this and I am trying to solve this using charge conservation. ...
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1answer
50 views

How to use output of NSolve for further calculation and than plot?

I am trying to plot the output using these linear equations but finding some difficulty. Here I am using the output of these linear equations and after that using them in another formula and after ...
2
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1answer
56 views

Vectorized RootFind for interpolated function

I've spent the last few days trying to vectorize my code to speed up root-finding on a grid. Apologies in advance if my code is poorly formatted. I have a fair amount of setup for the problem. It ...
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49 views

Table values of non trivial zeros of Riemann zeta function using integral form

I want to build a table values of non trivial of Riemann zeta function using the following function up to $ 10^4$ zero ,For all $s\in\mathbb{C}\setminus\{1\}$ the integral relation $$\zeta(s) = \frac{...
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1answer
44 views

Get the representation of {x,\theta} with the given equations

I am working with a Transfer funtion problem. I want to get the representation of {x, $\theta$} with the given equtions(below). In the equation x10 and x20 means the initial value of x1 and x2. all ...
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95 views

How to solve these equations without errors?

I'm a new user of Mathematica 12. I have to plot real and imaginary solutions of two equations, eq1 and eq2, which contain the ...
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2answers
87 views

Need help in Fourier Transform

My code takes long time without results even with Apart function for this simple function. ...
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0answers
39 views

Problema simulating FindRoot

I am writing a procedure that simulates the findRoot built-in function using the same code that appears at chapter 6 of $\textit{Programming in mathematica}$ by Paul Wellin. The code is the following....
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2answers
43 views

Eqaution solving & checking program! [closed]

Slove the eqaution 2x^2+5x+1=0 in real number range. Then, by putting it in the equation, check if that is correct. (Use NSlove, Chop, and substitution) I want a code which uses above three ...
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1answer
62 views

How can I calculate this integral?

I would like to calculate the integral in equation pol[x] if the quantity is positive or negative. ...
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3answers
77 views

Need help with finding a matrix

Could anyone please help me find a 4 by 4 matrix A such that A.Transpose[A] exactly equals the following matrix: ...
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2answers
149 views

InverseFourierTransform takes forever

I am trying to find InverseFourierTransform of the following function, but the code below does not give me a result. I do not get any error messages but the calculation just does not end. Any Help? ...
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1answer
38 views

Assign variable to solve [duplicate]

I would like to assign my result from equation. I tried /. and := but it gives me empty variable. How can i fix it?
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3answers
78 views

System of non-linear equations - Symbolic solution

I've been running this code for more than 12 hours and still can't find a symbolic solution for this. Maybe there is a way to simplify it or something might be wrong with the code. Do someone have a ...
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2answers
53 views

Finding the roots of a vector function: Sin[x + y], Cos[x - y], x^2 + y^2 - z

{Sin[x+y],Cos[x-y],x^2+y^2-z} I've tried to use the FindRoot function, which gives me an answer. However, it also says "Failed ...
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98 views

Problem in solving system of equations using “Solve”

I have an equation in its normalized form as: $\frac{v(x)}{V_{cc}}=C_1\cos qx+C_2\sin qx+1+ \frac{q^2}{1-q^2}.\frac{V_R} {V_{cc}}\sin (x+\phi)$ Where $$q=\frac{1}{\omega\sqrt{LC}}$$ With the ...
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1answer
51 views

Grid for NDSolve

i want to get the output of NDsolve in the form of a tbale/grid that can be exported to .xls/.csv. NDSolve[x'[t]==Exp[t], y'[t]==cos[t], x[0]=0, y[0]=1,{x[t],y[t]},{t,0,10}] I am expecting an output ...
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1answer
52 views

Solve variable inside Module

Suppose I have a Module in which I use Solve[]. If I make the solve variable local, I get this: ...
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0answers
4 views

Assigning a solution to variables [duplicate]

I have solved my solution and it has been appeared, it is C1, C2, C3, C4 but when I call C1 again (%13), program shows me that C1,... is not assigned. How can I reapair that ?
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21 views

Global maxima and minima for a multivariable function (brute-force search)

I have a function $p(\theta,z,t)$ defined at the end of this question. I am trying to do two things here: Find the global maximum and the global minimum of $p$, for some specific values of $a$ and $d$...
2
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1answer
59 views

Is it possible to use `ContourPlot` for specific eigenvalue of a large matrix Mn(x,y)?

I have a large matrix, say En En, as a function of two variables x and y which has ...
4
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2answers
107 views

Numerical Landau Damping dispersion relation, Principal value numerical integral

Greeting, I'm searching to solve numerically the dispersion relation for Landau Damping, it is: $$ 0=1+\frac{1}{k^2}\int_{-\infty}^{+\infty} \frac{\partial_v f_{0}}{w/k-v}dv$$ Which then can be ...
2
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1answer
51 views

Solving multiple integral with symbolical limits [closed]

I am trying to solve a double integral, though I am not sure how I could potentially handle the symbolic limits. I have attempted the following code: ...
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0answers
54 views

Define a variable to satisfy $x^3 = -x$, then sum to find exponential

I'm wondering if it is possible to tell Mathematica that my non-commuting variable satisfies $x^3 = -x$ such that it can compute $\sum_{n=0}^\infty \frac{(Ax)^n}{n!} = e^{Ax} = \cos A+ x \sin A$ with ...
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2answers
128 views

Solving for the coefficients in a nonlinear equation according to constraints

How do I solve for coefficients in a nonlinear equation? E.g. Consider $p(x,y,z,t) = e^t(ax^2 + by^2 + cz^2)$ and I seek the values of $a,b,c$ which make $p\approx0$ at all the points $(x=r\cos\theta,...
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3answers
133 views

Solve / brute-force for parameters that drive a function to zero at specified points

Edit: Made question a lot easier to read. Simple example. - Consider $p(x,y,z,t) = e^t(ax^2 + by^2 + cz^2)$ and I seek the values of $a,b,c$ which make $p\approx0$ at the point $(x=r\cos\theta,y=r\...
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2answers
43 views

Does anyone know how to interpret this solution to a rational equation? [duplicate]

I was trying to sove this equation to obtain b as a function of a, but I do not understand the answer that Mathematica gives to me. What are the solts # for? and the &,1 in the end? Equation <...
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0answers
55 views

Solve no longer working

I have defined four functions ...
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1answer
49 views

Understanding Root and Solving higher degree polynomials [duplicate]

I have trouble understanding Root in Mathematica. For instance: Solve[x^5 + 2 x + 1 == 0, x] gives me a strange solution ...
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1answer
100 views

Solving a system of trigonometric equations. with NSolve

Is numerical solving of the problem in the picture below even possible? Edit: The code does not output anything, it just runs for 20min+ ...
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46 views

Zero of a function with Davidon–Fletcher–Powell method

I have a problem with this code. I need to find a zero of a function with Davidon–Fletcher–Powell method, which is known as Quasi Newton's method for finding a zero of a function.This is the given ...
2
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1answer
46 views

Using Solve[] in Module

Clear[x, y]; function2[eqn3_, eqn4_] := Module[{x, y, sol}, sol = Solve[{eqn3, eqn4}, {x, y}]; {x, y} /. sol] function2[y == 3 x, y == x^2 - 4] I want it to ...
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1answer
45 views

Finding an instance of a parametric equation that intersects given points

So I have this equation for a circle centered at the origin that has some orientation in 3D space. ...
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1answer
31 views

Recursion limits and singular Jacobians [closed]

As a warm-up exercise, I am trying to solve the following system of equations: $$ p = \frac{\text{exp}(q)}{\text{exp}(q) + \text{exp}(1 - q)}, \hspace{0.5em}q = \frac{\text{exp}(1-p)}{\text{exp}(1-p) ...
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1answer
142 views

Help with solving an equation [closed]

Could anyone please help me find the real solution(s) to a system of equations, or could anyone please help me find an effective solver to solve it? The function ...
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0answers
24 views

A: Symmetry-finding packages [duplicate]

I am facing the problem to derive the overdetermined system of equation and it's solutions. I want to download the MathLie package for symmetry analysis which is mentioned in G.Baumann's paper.
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1answer
77 views

Plotting a differential equation with boundary conditions

I have a problem with numerical calculation and plotting of differential equation. Now I set a complicated region to set a boundary condition: ...
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0answers
56 views

How should I solve this Logarithmic equation analytically? [duplicate]

Is there any way to solve the following equation analytically? ...
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1answer
69 views

Why can't I use FindInstance to find more than one solution when I know they all exist?

For example, it is easy to find one solution for this code: ...
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0answers
53 views

How to define an Intermediate Variable [duplicate]

I want to find the relationship between several parameters. But I don't know how to define an Intermediate Variable. For example: I want to know the relationship between x and {y,z} which will satisfy ...
4
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0answers
56 views

Indicate Unit Vectors in Solve

I'm solving a system defined by two rays. The rays originate from two points {x,y,z} and {x,y,z-h}. They go in directions (unit ...
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0answers
75 views

Runge-Kutta on coupled equations

I'm still pretty new to Mathematica and I'm having a few issues solving these coupled equations. I've attempted using NDSolve with method "ExplicitRungeKutta" as well as with no method, and have had ...
1
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1answer
54 views

Find the number of upvotes on my reddit post

I posted a video on reddit that has more downvotes than upvotes. Rather than showing a negative symbol, it displays a zero. It says I have 29% (edit: now 33%) of the votes were upvotes which I guess ...
4
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1answer
56 views

Finding a Rational univariate representation (RUR) for a Polynomial System

According to Wikipedia, a RUR of a zero-dimensional system consists in a linear combination of the variables, $x_0$ called ''separating variable'', and a system of equations : \begin{cases} h(x_0)=0\\...
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1answer
47 views
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0answers
58 views

how to solve error linear equation system

I can't run the code below because there is some error. How to solve the "null" problem and show answers exactly with convergence. The code following: ...
6
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1answer
181 views

Solve can't solve my trigonometric equation—why?

I have the following equation for epsilon $2 |\alpha_{n,ch}|=\epsilon+\cos^{-1}(\tan(\frac{\pi}{4}-\frac{\epsilon}{2}))$, where $\alpha_{n,ch}$ is a negative constant (e.g. -0.769) I tried to solve ...
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32 views

Calculation of algebraic sets using sequences

I am attending algebraic geometry and we are dealing with algebraic sets in the polynomial algebra. I wanted to make a code that receive some polynomials and give me a certain decomposition of its ...

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