Tagged Questions

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

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NDSolve is running an extremely long time: how can I save the existing data?

I am trying to solve a PDE by the following code. It takes 1 hour or so to reach t=25.72 but about 20 hours to reach t=25.72404031638060174049337306126853310997. Actually, the time step is extremely ...
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Proving large inequality in 6 variables

I have arrived at a very large inequality in 6 variables that I would like to prove is true. The command I have tried is the following: ...
175 views

How can I get all solutions of a system of equations with Reduce?

The post What is the difference between Reduce and Solve? discusses the difference between Reduce and Solve. Now, with the ...
297 views

Fick's Law over Implicit Regions

I'm trying to solve 2D Fick's law of diffusion from the boundaries of a triangle (future shapes will include more complex implicit regions). I'm able to model diffusion without time in complex ...
151 views

Defining Solutions to FindRoot a functions of parameters-Part II

Here's a similar question as the the preceding question with the same title, but this time with vectors, which I need to use. I followed the suggestion in the answer the the previous question, but it ...
81 views

Weird behavior when solving a simple physics problem

I have the following code in Mathematica that represents two balls being thrown, one with a velocity v10 (6 in this case) and another ball thrown with a velocity v20 (its just dropped) one second ...
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Defining solutions to FindRoot as a function of parameters in Mathematica

This works: f[a_] := x /. FindRoot[x^2 - a == 0, {x, 1}] f[3] (* 1.73205 *) I need this to work, but it doesn't: ...
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How to exract the roots from “Roots”? [duplicate]

Given how the output looks like, as in a set of "==" assignments, is it possible to extract specific roots from the output of, http://reference.wolfram.com/language/ref/Roots.html ? And then do a ...
1k views

How do I write nested for-loops?

Looking through the reference.wolfram, I couldn't see an example of how to write a multiple line "for" loop in Mathematica. I need to nest many for-loops in such a way I can do many things in the ...
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Why do I get this error (solving a system of equations)? [closed]

I use the following code ...
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How to contourplot a function defined via findroot? [duplicate]

when I use contourplot, the system will simplify the expression first with its parameters holded. However some expressions can not be simplified first without inputting parameters, for example, ...
203 views

Solving Non-linear System of Equations

I need to get a symbolic solution to a system of non-linear equations (equation 8 is non-linear), but Mathematica is running for ever and gives no answer. Is there another way to get the solution? My ...
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Why does this function inside FindRoot fail to evaluate?

Can someone help me understand why function mu found below does not execute when everything before it seems ok. ...
188 views

How to assign equation solutions to variables [duplicate]

I have 12x12 Matrix with which I have to solve the equation below: ...
74 views

Searching in parameter space for a given number of solutions

I have this problem : I have some function g[a,b;x], where a,b are parameters and x is a variable. I know (graphically) that an equation g[a,b;x]=0 has zero, one or two solutions. I want to keep 'a' ...
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Equation Solving

As I stated in this question I want to solve a series of equations while setting some rules such as q[2]->1 or q[2]->3*10^-4. However, what should I do if I want to set another rules to my input? I ...
128 views

Non Linear Equation Solving with Matrices

Suppose I have the following matrix equalities: A=X, B=Y where the left-hand side matrices are numeric and the right hand side contains non-linear combinations of unknowns. Since I have quite a few ...
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How to find only the negative Imaginary solutions and positive Real solutions?

Following this post Help Please : Error in plotting the solutions of FindRoot , I want to plot only the negative Imaginary solutions Wi(K)<0 and positive Real solutions Wr(K)>0. Please, how do it? ...
66 views

Finding a solution when there are two piecewise functions at play

The goal is to mathematically figure out where is the point when the both of the diagrams are the same distance to the Y-axis. The solution to such a problem can be obtain quite easily by just ...
416 views

Apart for complex roots?

Let p[x] be a polynomial in x and consider the partial fraction decomposition of 1/p[x]. ...
99 views

Solving A Series of Equations

I want to find the solutions of a series of equations as I stated in this question before. I understood how to solve the equations by maximizing the value of a variable but now I want to find the ...
I am doing this mathematical problem $c*G_{vv}+ d*G_{u} + e*G_{v} +f*G=0$, where $c, d, e$ and $f$- are constant coefficients. I already know that this is second order PDE and we classify it by ...