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

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0
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0answers
4 views

Significantly different results between Mathematica and Wolfram Alpha with large radicals and small numbers

I have some code which involves tiny numbers being put to the power of very large numbers. The function I'm looking at is $\varphi = \omega(T) \left(1 - (1 - \epsilon)^{n_{e}(T)} \right)$ when ...
4
votes
2answers
208 views
2
votes
0answers
15 views

Finding degenerate solutions to cubic equation, to find touching points in bandstructure

I have a cubic equation (corresponding to the band structure of a physical system) given by w in the code below. ...
4
votes
1answer
235 views

Numerical errors/inaccuracies in ProductLog

Context In cosmology, a fairly accurate model to describe the gravitational potential, $\psi(r)$ of dark matter halos is given by $\psi( r)=\log(1+r)/r$. ...
2
votes
1answer
115 views

Solving a system of weird equations

I'm trying to have Mathematica solve a system of equations for a friend's work in Computer Vision. I'm essentially going in blind to this and am not very familiar with Mathematica syntax, so would ...
0
votes
1answer
57 views

Removing imaginary and negative results from Solve

I have been trying to solve a series of equations that I know have real positive values for the unknowns (they all have real world analogues and they are not linked to a frequency domain) but despite ...
15
votes
5answers
759 views

How to make a Line[] with no end?

I'm trying to do this: In this graph, the secant points are aproximated in order to become the tangent, it seems I need some kind of function which plots a line based on two points and it's points ...
1
vote
0answers
35 views

DSolve -> no results

I am trying to solve a system of differential equations. ...
0
votes
3answers
54 views

NSolve not solving [on hold]

I've been working on a Newton Cooling equation problem for my diff equ class and cannot get NSolve to solve this equation. I've plugged it into Wolfram Alpha and my ...
1
vote
2answers
186 views

Problems finding intersection points between line and generic function

I'm trying to find Intersection points between a line, which is given by 2 points, and a generic function (I want it to be able to handle polynomial functions, circles/ovals, lines and all ...
2
votes
1answer
105 views

Equation involving hypergeometric functions

I want to solve this equation but nor NSolve nor Solve are able to do this. ...
10
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1answer
136 views

Using Simplify on a consistent system returns False

Bug introduced in 8.0 and persisting through 10.1.0 or later It's late, but am I missing something here? Why should two independent equations, which together are consistent, ...
0
votes
0answers
164 views

Why does my calculation of a probability take too much time?

I am calculating the value of the following function for given argument values: ...
14
votes
3answers
352 views
+200

Solve a trig equation system

Background of the problem In the same plane, P is a fixed point, A,B,C are moving point, PA=a, PB=b, PC=c, find the maximize perimeter of △ABC. let ∠BPC=A, ∠CPA=B, ∠APB=2*Pi-A-B, then the ...
0
votes
1answer
73 views

Elements inside arrays seem to be strings rather than signed numbers

When I have code like b = Array[Subscript[be, #] &, {3, 1}] b = b /. {Subscript[be, k_] :> Subscript[-be, k] /; k > 1} I am noticing that Mathematica ...
5
votes
2answers
244 views

When does the real part of Zeta vanish on the critical line?

This seems to be a quite a simple problem but I cannot make it work. I am trying to find all values within a given range for which the real part of the Zeta ...
4
votes
1answer
368 views

3D Plot of The Riemann Zeta Function

I am a new user and i would appreciate your help to visualize the 3D of the following function. Edit I tried this ...
0
votes
0answers
45 views

Solving a system of nonlinear equtions [on hold]

I'm trying to solve a system of nonlinear equations which consists of 12 variables and 12 equations. A solution is obtained, but with an error. FindRoot::lstol: The line search decreased the step ...
2
votes
2answers
130 views

Solving for any one variable in a formula given values for all the others

Suppose I have an equation relating a number of variables and I know the values of all but one of them. Using the equation and known values as input, is there a simple command (built-in or otherwise) ...
0
votes
1answer
343 views

How to use `FindRoot` to solve an equation containing a parameter?

I'm trying to derive some of the results of the following paper: Electrodynamics of semiconductor-coated noble metal nanoshells, JT Manassah - Physical Review A In the paper there is matrix $\mathbf ...
0
votes
1answer
101 views

In which condition releated to thee coefficients some equation has a solution

Please excuse me if the question seems to commonplace. Can Mathematica give a response to this question: In which condition related to the coefficients $c>0, \, n\geq 2, 0<p<1,\, a>c$ ...
0
votes
1answer
192 views

How to calculate the unknown quantity in an infinite series?

I'd like to calculate x value in this equation. Basically, I tried to 2 types of method which are FindRoot and NSolve. But, I have failed the calculation caused by these errors up to now. If ...
3
votes
1answer
44 views

Using result of Solve in further calculations

I'm trying to make a code for Gauss-Legendre quadrature. First I find the roots of the polyinomial with roots[n_,x_]:=Solve[LegendreP[n, x] == 0] Then I need to ...
7
votes
3answers
175 views

How to solve for the intersection points of two ellipses?

I have a parametric equation of two ellipses as follow $\begin{cases} x=a_1 \text{sin$\theta $}+b_1 \text{cos$\theta $}+c_1 \\ y=d_1 \text{sin$\theta $}+e_1 \text{cos$\theta $}+f_1 \\ ...
21
votes
3answers
917 views

Does Mathematica have a built-in tool that allows one to operate on both sides of an equation?

Geogebra has a very neat CAS view that allows one to solve an equation step by step in the following fashion: $\quad \quad \quad \quad \quad \quad \quad \quad \quad $ You type an equation and ...
0
votes
1answer
71 views

Solving non-linear ODE analytically in mathematica [closed]

I would like to solve the following differential equations $${dx\over dt}=\beta x-{{(C-x)^2}\over 4k} ,t\in[0, T]$$ where $\beta$,$C$ and $k$ are constant values. Also, the folowing terminal ...
21
votes
7answers
5k views

About multi-root search in Mathematica for transcendental equations

I have some questions for multiroot search for transcendental equations. Is there any clever solution to find all the roots for a transcendental equation in a specific range? Perhaps ...
1
vote
1answer
38 views

Reduce with for all and implies

I have the following question. p1 = a (1 - c + a) p2 = b (1 - c - b)/((1 - b)^2) v1 = (x^1.5 - 3*x)*p1 v2 = x*p2 I want to find x ranges which makes v1>v2 under ...
1
vote
2answers
81 views

Find all roots of a function with parabolic cylinder functions in a range of the variable

I want to find all roots of a function involving Parabolic Cylinder Functions. In what follows, I define 2 variables $\xi1$ and $\xi2$, which in turn depend on $\omega$. My function is then defined as ...
1
vote
0answers
171 views

Solve set of non-linear equations with least-squares-fitting - constrain results?

I'm trying to solve a set of functions to determine the material properties from a set of measurement values. (To set up this method I just want to fit my model with some already calculated data). My ...
0
votes
0answers
22 views

Why does `NSolve` not solve this system of equations on a bounded domain?

I have three functions $E1,E2,E3$ of $t1$ and $t2$. The expressions are slightly complicated and involve trigonometric functions. For clarity purpose, they are given at the end of the question. I ...
1
vote
2answers
63 views

What is the role of the pattern object in this implementation?

In the documentation I found a nice idiom which allows me to do model fitting with interpolating functions. I think this kind of thing is amazing and a credit to the utility of an environment like ...
1
vote
1answer
119 views

Solve a system of non-linear equations

Is there any way to get an exact solution a system of non-linear equations? The system I would like to solve is: $\quad \quad \begin{eqnarray} h_{1}x_{1}=c_{1}\\ h_{2}x_{2}=c_{2}\\ ...
1
vote
1answer
121 views

Eliminating parameter from parametric equation [closed]

In Mathematica Online I tried: Eliminate[{x == t + t^3, y == t - t^3, z == 1 + t^4}, {t}] ...
2
votes
1answer
153 views

How to properly interpret a seemingly contradictory result in Mathematica?

I have a problem with interpreting the results of my notebook outputs. It is important that I do not err with the interpretation. Here is the full input: ...
1
vote
1answer
77 views

How can I solve an equation independent of a variable? [duplicate]

Let's say I have the equation $$ ax + b = 0 $$ and I'd like to find a solution that doesn't depend on $x$, so here the solution is obviously $a=b=0$. I could solve this using ...
2
votes
0answers
47 views

Problem with plotting a function that calls FindRoot

I am having difficulties in plotting the solution of FindRoot to solve 4 variables. I defined a function and then tried tp plot it, but got an error message ...
0
votes
1answer
404 views

Trying to solve a transcendental equation involving Bessel functions

I've never used Mathematica before and am trying to numerically solve equation (12) from this paper. Ideally I'd be able to find the smallest value of $x_{n\nu}$ for $\exp(-kr\pi)$ close to 1, and ...
1
vote
2answers
81 views

Why does Mathematica not evaluate the difference recurrence using `RSolve` or `RecurrenceTable`?

Mathematica does not evaluate the following recurrence of two variables using RSolve and only echoes the input: ...
0
votes
2answers
60 views

Solve returns empty list / running forever

Update: I made a mistake before and corrected the sign in code below in case people wonder what some comments mean. Thank you for those who answered. But I should have said that this is only part of ...
20
votes
4answers
3k views

How to get intersection values from a parametric graph?

I have this graphed: ParametricPlot[{2.4*Cos[t] + 1.6*Cos[3 t/2], 2.4*Sin[t] - 1.6 Sin[3 t/2]}, {t, 0, 4*Pi}] It is a star, and the lines cross each other ...
1
vote
1answer
105 views
0
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0answers
56 views

Inverse Superposition

There are 4 tables that, I have written them as bellow: (m, n, s, and r are orthogonal basis. r.r=n.n=m.m=s.s=1, and m.n=n.r=...=0). a's, b's, c's and d's are coefficients and are numeric values. ...
2
votes
1answer
113 views
1
vote
2answers
97 views

Solve[ ] doesn't work with transcendental equations

How to solve x^5-sinx=0 in mathematica? I try in this way: Solve[x^5 - Sin[x] == 0, x],but t doesn't work.
1
vote
4answers
3k views

How can I use assumptions with FindRoot?

I have something like FindRoot[f[x], {x, a}] Now I want FindRoot to constrain the solutions to 0 < x < 1. How can I ...
7
votes
6answers
438 views

Finding where two parametric paths cross?

I have been looking through other parametric equations questions and am still unsure where to start with this one. I am given two functions: ...
0
votes
3answers
69 views

Problems with finding the real solutions of equation

I am trying to find real solutions of equation using Mathematica 8.0 but there is some problem I don't know how to explain. For example, for the input ...
0
votes
1answer
35 views

Unexpected ReplaceAll behavior with NSolve

I ran into some unexpected behavior using ReplaceAll with an equation of motion using NSolve (or Solve, also). First solving for the initial velocity v0: ...