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

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3 views

Tracking solutions over a Brillouin zone

Thanks to @bbgodfrey I have a function that finds the two solutions to a set of equations bounded by a hexagonal region (corresponding to the Brillouin zone). It takes the angle ...
0
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0answers
13 views

RSolve with integrations

I want to solve this question with Mathematica. $$T_0(t)=c(t),\quad T_n(t)=a\int_0^t T_{n-1}(s)\, \mathrm{d}s+b(t).$$ Is it possible to solve $T_n(t)$ with ...
0
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1answer
43 views

Add assumptions to Solve command

I want Mathematica to solve the following by assuming the part within the Log function, which is ...
0
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0answers
57 views

Difficulty solving an equation involving a couple of different powers

I have this semi-complicated equation to which I want to find an analytical solution for $\epsilon$. The equation is a s following: $$a^2 (2 b k \epsilon \sqrt{1 - \epsilon^2/b^2} - 2 c k ...
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1answer
60 views

Equation solving problem [on hold]

I have this code: ...
0
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0answers
52 views

I made my own equation, how do I know if it already exists? [on hold]

I made my own equation after playing around with some numbers. So I started to look for the equation to be sure I made it first. I googled and searched for it almost everywhere but couldn't find it. ...
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0answers
23 views

Convert the output of solve into equality [duplicate]

I know this is has been asked before but seriously, none of the ones I checked helped because they referred to a single variable assignation. Apologies if this is a duplicate. I have many variables ...
0
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1answer
117 views

Formatting an equation: X^Y to pow(X,Y)

I am trying to solve for the intersection of two circles with arbitrary centers and arbitrary radii. ...
0
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1answer
61 views

numerically solving

I am trying to solve for [Lambda] as a function of a (unknown) from this expression ...
0
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1answer
43 views

Setting the solutions of an equation as a variables [closed]

This is probably a simple question, but i couldn't find a solid answer. So i have an equation Solve[{F[x, y] == 0, G[x, y] == 0}, {x, y}] but i want to use the ...
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3answers
78 views

Finding roots of transcendental equation and collecting into a list

I am working on a physics reserach project for school and I have run into some troubles working Mathematica. I am a fairly inexperienced mathematica user so any help would very much be appreciated. I ...
6
votes
2answers
163 views

How to reverse irreversible function in Mathematica?

How to reverse formula $y(x)=x (\frac{1}{sin \frac{\pi x}{2}})^\alpha$ i.e. express it as $x = x(y)$ in Mathematica? I did this way ...
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2answers
50 views

RegionPlot after Reduce

I have a problem in this form To solve this I have tried this f1[y_] := 2 - (y - 1)^2; f2[x_, y_] := x + 1 - (y - 2)^2; f[x_, y_] := Max[f1[y], f2[x, y]]; The ...
3
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3answers
107 views

Reduce gives wrong solutions

Given the follwing system of equations eqs = { x/(x - 2) - 4/y == 1, x/(2 + 1/y) == y/(3 - 1/x) } Although the domain of this system does not contain ...
0
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0answers
58 views

ODE using Mathematica [closed]

A man throws a pebble straight up. Its height $y(t)$ satisfies the differential equation $y"+\gamma y'=-g$, where $g$ is the acceleration of gravity and $\gamma$ is the damping rate due to frictional ...
-2
votes
1answer
50 views

Solving fifth order polynomial equation [closed]

I am trying to solve this equation: 1/s^3 + 3s^2 + 4s + 1 But I am not able to solve it. A little help would be appreciated. P.S: I am new to Mathematica and I ...
2
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1answer
61 views

Faster variant of Reduce for finding zeros of holomorphic functions in a region

I'm currently using Reduce to find zeros of a function in a region on a complex plane: ...
-1
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0answers
44 views

What is this syntax, [[1, 1, 2]]? [closed]

Ndsol = Solve[{D[y[z, n], n] == w, w == we(1 - (p - pe))}, {we, w, n}] nd[z_, we_, p_, pe_] = Ndsol[[1, 1, 2]] The what do the ...
4
votes
1answer
51 views

Sequential System of Equations

I’m trying to set up this system of equations that sequential feeds into itself. I have these 2 equations I’m running. I’m new to Mathematica so I have no idea how to even start this. The basic idea ...
0
votes
1answer
50 views

Roots of a transcendental equation

I need to find the 50 first roots of a transcendental equation. I use Table and FindRoot, so I find repeated positives and negatives values in a list, but I want only the 50 first positives and ...
0
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0answers
61 views

First Order Conditions

I am new to Mathematica so I am not sure if this is correct. I have setup up a Lagrangian and I am trying to get the FOCs of this problem. However, it does not seem to work. Any help would be much ...
0
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0answers
128 views

Solve doesn't solve my transcendental equation

I want to solve a geometry problem. To do this, I need get formula for "d" in the equation: ...
1
vote
1answer
73 views

Improving Performance - Finding Polynomial Roots [duplicate]

I'm fairly new to Mathematica. In the past, my usage has mostly been limited to solving the occasional equation, making some plots, and working with small scaled statistics. None of these have been ...
0
votes
0answers
65 views

What does it mean when FindInstance returns unevaluated?

According to the documentation, FindInstance[] return the empty set when it does not find a solution and one of the examples claims that this is proof that no solution exists. So if FindInstance[] ...
-2
votes
1answer
46 views

Solve on parametric equation produces inequal results

I have a parametric (parameter t) equation in two dimensions (vectors). s = Solve[pt[t] == qt[t], {a, b}] Both pt and qt are parametric lines using a and b as ...
0
votes
1answer
106 views

Time evolution of a wave packet from the time-independent Schroedinger equation [duplicate]

Starting off with the time-independent Schroedinger equation (TISE) $\quad \quad -\frac{\hbar^2}{2m} \nabla^2 \psi + V(r, \theta) \psi = E\, \psi,$ I would like to study the time evolution of an ...
0
votes
2answers
38 views

Expand “hierarchical” system of equations

I have a system for equations that is structured hierarchically: - Level 0: these are base variables that I can measure from a process (e.g. a,b,c) - Level 1: these are variables derived from Level 0 ...
1
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1answer
109 views

Approaches to solving non-linear systems of equation with assumptions

The specific type of system looks as follows: \begin{align} (r-r')x+4d_1 x^3+4d_{12}xy^2 &= 0 \\ (r+r')y+4d_2 y^3+4d_{12}yx^2 &= 0 \\ \end{align} Where $r,r',d_1, d_2, d_{12}$ are all real ...
0
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0answers
47 views

No solution for a system of equations

I am a newbie in Mathematica and I face a problem in my attempt to solve a system of equations. The system is the following: ...
1
vote
1answer
144 views

How to plot the graph of the equation F[x,y]=0 if y is real number, x is complex? [closed]

I have an equation F(x,y;a,b,c,...)=0, where x and y are variables, a,b,c,... - parameters. y is a real number, x - complex. For every given y I need to solve this equation, i.e. to find Im(x) and ...
1
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1answer
75 views

Solving equations bounded by a region

Straight to the point I have a function ...
0
votes
1answer
32 views

Strange behaviour of Append [closed]

I have the following situation and I completely do not understand why the second system can be solved but the first (of the same equations, as it seems) cannot. How is it possible? ...
0
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0answers
26 views

Problem evaluating function

Hey there I am missing the trick in evaluating following problem so that mathematica first solves the derivative of the legendre polynom and just after that it solves the whole thing for value 1 ...
0
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1answer
23 views

Many NSolves to interpolating function

I have an expression of the form: expr = TerribleNumericalFunction[U[p]] == SimpleFunction[p] The Simple function is a ...
0
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0answers
37 views

Solving Lagrangian (4 vars to solve for)

I'm a bit new to Mathematica, but here's what I've got: ...
0
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0answers
68 views

Solving symbolically large system of underdetrmined linear equations

I would like to find matrices 3x3, say A, B, C, such that for all symmetric matrices X, with zero trace, one has: $$AX_1+BX_2+CX_3=0, AX_2=BX_1, AX_3=CX_1, BX_3=CX_1$$ where $X_i$ denotes i-th row (or ...
0
votes
1answer
48 views

Finding gradient of equiangular (logarithmic) spiral

I encountered a problem in determining the gradient in cartesian coordinates (x,y) of a logarithmic spiral (or equi-angular spiral) profile. The log-spiral definintion is as shown below (similar to a ...
1
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1answer
75 views

Complicated equation solving

I want to find the maximum point or optimal value $y$ of Rx1[y_, a_, b_]. ...
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0answers
72 views

Solve does not work for an equation for which I know a solution exists

I have a simple equation, which I want Mathematica to solve for x in terms of y. The code runs for days. When I assign values to ...
2
votes
1answer
66 views

Stability Boundaries via Routh-Hurwitz Criterion

I'm attempting to determine the stability boundaries of a 2nd order system via Routh-Hurwitz stability criterion. That is to say, I need to compute when a polynomial, which is in terms of variables ...
0
votes
0answers
23 views

Some more efficient form to calculate the order value

This takes a long time, any idea how accelerate Reduce[x^(2 x^2 - 2 x) - 1 == x , x] k = x^2 + x^-2 k = ?
0
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2answers
60 views

Diophantine and odd

need to resolve this Diophantine equation, but with the condition that a, b, c belong to the set of odd numbers from 1-51, as I write this condition in the code ...
0
votes
2answers
78 views

Find smallest integer that satisfy a system [closed]

f[m_,n_]:=-205 m^2-(672m)n+324(n^2) I want to find the smallest positive integer M such that all of the numbers f(m,n), for m=1,2,...,M and n=1,2,...,M are ...
2
votes
1answer
108 views

Can Mathematica solve this type of recurrence?

I have the following recursively defined equation: ...
1
vote
3answers
132 views

Find value of x such that x! less than or equal to 1000

I am trying to find the maximum value of $x$ such that $x! \leq 1000$. I tried the following: NSolve[Factorial[x] - 1000 == 0, x] but I got this message: ...
0
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0answers
56 views

Solve[..] does not solve the equation? A bug?

I tried to get the values of CosTheta where the expression is zero and store theses in sol. ...
0
votes
1answer
41 views

Finding the intersection of two graphs [duplicate]

I'm having difficulty with finding the intersecting point of two graphs. Here is what I have done so far: Plot[{8*n^2, 64*n*Log2[n]}, {n, 0, 100}] which produces ...
1
vote
1answer
53 views

Plotting solutions of systems in complex plane

I'm interested in plotting solutions of systems of polynomials in the complex plane, in the following way. Let $f_1,\ldots f_s$ be complex polynomials in variables $x_1,\ldots x_n$. I know how to ...
2
votes
4answers
116 views

Using ArcLength in Mathematica 10 using absolute values

With Mathematica 10, I can nicely plot: y = x^2 - 4 Abs[x] - x But I have not been able to use ArcLength to get the length of ...
1
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1answer
86 views

Solving ODES in order to find unknown constants

I am trying to solve a set of ODES which represent a second order consecutive chemical reaction. ...