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

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1
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0answers
34 views

FindRoot::nlnum & Interpolatingfunction

I want to solve a system of differential equations and find a point where the solutions cross. So four steps: 1. Solve the system of differential equations: ...
1
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2answers
59 views

Solve equation with Log[s]

When i try to solve the following equation, i get error message that "Solve::dinv: ...."due to the presence of Log[s0] term. How to solve this? the code is given below: ...
4
votes
1answer
77 views
0
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6answers
250 views

Roots of a characteristic equation. Can Mathematica solve it?

I have been using Mathematica for a few years, but with basic things. Now I need to find the first 10 roots of the following equation: ...
2
votes
1answer
90 views

Putting as many expressions as possible equal to zero

Say I have a list of expressions involving many different variables. I would like to see how many of the expressions I can set equal to zero thereby solving for some of the variables in terms of the ...
1
vote
1answer
41 views

How to find function existence border

I have a function like this f[x_, a_] = Log[-x - a]*(-x - a) + Sin[a]; this function does exist if x > a because of Log[]. a - parameters. if I plot a few graphs ...
3
votes
1answer
169 views

How to tell Solve[] to satisfy as many constraints as it can?

Is there any way to tell Solve (or something similar) to return values for variables that solved as many constraints as it happened to satisfy? Edit: I had ...
2
votes
1answer
77 views

How to estimate the running time of a programme on mathematica [closed]

I am solving a system of 6 linear equations containing six unknowns using mathematica. It is taking too much time and still running after 3 hours. can I estimate the approximate running time? Is there ...
3
votes
2answers
184 views

the exact real solutions of cubic polynomial?

Such as the equation:$x^3-5 x+1=0$, according to the cubic discriminant we know it has three real solutions. We can also find the exact expressions of them from Mathematical handbook. However, by MMA ...
0
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0answers
46 views

Problems solving differential equation with ParametricNDsolve for certain parameters

I'm working on a simulation of a physical problem for a few weeks now and I'm starting to get really frustrated about it. The problem itself is the stationary case of the heat diffusion equation in ...
1
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0answers
321 views

Automatic inverse for Lambert’s Azimuthal Equal-Area Projection

I’m interested in finding closed-form inverses for map projection equations in general (of course, this is not always possible). I’m hoping Mathematica can help me with some of the trickier ones. As ...
1
vote
0answers
51 views

Can Mathematica give the solutions to x^n - 1 = 0 in their radical form [duplicate]

If I input: Solve[x^3 - 1 == 0] Mathematica returns: {{x -> 1}, {x -> -(-1)^(1/3)}, {x -> (-1)^(2/3)}} I want to see the roots expressed as radicals for ...
5
votes
3answers
452 views

Writing Mathematica's Root function output in a academic paper form

I need to write the following (which is the result of a Solve command I ran in Mathematica) in an academic journal paper: ...
3
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2answers
79 views

Solving system of equations in Mathematica

I am unable to solve this system of equations in Mathematica. Where the third equation takes value (on the right hand side) from 0.00001 to ...
0
votes
1answer
67 views

Is it possible to stop NSolve when it finds a single root [closed]

I have a system of nonlinear algebraic equations with following property: if $(x_1,x_2,x_3,x_4,x_5,x_6,x_7)$ is a root of the system, so any its permutation is another root as well. My system contains ...
4
votes
2answers
183 views

Solve System of Equations with Constant Ratios

I'm currently trying to use Mathematica to solve a problem for my fluid mechanics class. I need to solve the following system of 3 equations: $$\begin{align*} \dfrac{h}{a} &= \cot ...
0
votes
1answer
78 views

Transforming from implicit Cartesian form to a parametric form [closed]

First equation $((1.2 x)^2 + (1.4 y)^2 - 1)^3 - (1.3 x)^2 y^3 == 0$ I wanna transform it into a parametric equation. I spent a much of a day working on it without success. The equation describes the ...
3
votes
1answer
89 views

Trying to find a temperature profile with a nonlinear 2nd order ODE. NDSolve very sensitive to seemingly arbitrary constant

I am trying to solve this differential equation for a heat transfer problem: \begin{equation} kt\frac{\partial^2 T}{\partial x^2} = \epsilon \sigma T^4, \ \ \ T(0) = T_0, \ \ \ \frac{\partial ...
3
votes
1answer
66 views

Reduce is not giving answers, only verifies it's true

I'm trying to find a range for {q1,q2} with the conditions listed such that U1R >= U1S ...
9
votes
4answers
262 views

How to find the next root larger than a specified value, numerically?

I would want to have a general-purpose, reasonably robust method of finding the next numerical root above a specific value of x. I'm stumped by the fact ...
0
votes
0answers
32 views

Solving for limit of integration with a piecewise function (FindRoot vs NSolve) [duplicate]

I am trying to solve for the limits of integration using a piecewise function. I'm doing this in a loop over a list of data, mostly because I'm not well-versed enough in Mathematica to make this a ...
1
vote
0answers
58 views

NMinimize / adding constraints

I have a quick question: in question:Solving an ODE with boundary conditions at infinity and 0//different problems, I asked for help concerning a differential equation- however, the whole solving ...
0
votes
0answers
27 views

find indeterminates (which are function of time) of an expression [duplicate]

Is there a function in Mathematica so as to find the indeterminates of an expression? When I used Maple, there was the function indets. Is there a similar function in Mathematica? Here an example ...
6
votes
1answer
140 views

Faster way to perform SameQ[Reduce[…], Reduce[…]]

I'm have some expressions that I need to confirm the equality of. SameQ[Reduce[...], Reduce[...]] works like a charm for the more simple expressions, however when ...
3
votes
1answer
67 views

Finding inconsistencies in a system of equations

I am a rookie in Mathematica and apologize in advance. Here is my question: Are there any tools, built in the program, of detecting inconsistency in a nonlinear system of equations? Whilst finding ...
0
votes
1answer
43 views

Use elements of a convex sets to solve equations [closed]

i try to do sth. like this A=Solve[{x>=5, y>=3, x<13,y<13} ,{x,y}] which gives me a convex set and then ...
5
votes
3answers
115 views

On Solutions of Diophantine Equation

By Mathematica, I try to obtain solutions of Diophantine equations such as: $$F_{n_1}F_{n_2}\cdots F_{n_k}+1=F_t$$ where the sequence $\{F_n\}$ is the Fibonacci sequence,$n_1 < n_2 < \cdots ...
-1
votes
1answer
76 views
1
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1answer
57 views

System solution [closed]

How to solve this system using Mathematica. eq1 := xsin[y] - 3.5 cos[y] - 4.5; eq2 := -xcos[y] - 3.5 sin[y] + .4; Solve[eq1, eq2, {x, y}] This does not work.
2
votes
2answers
72 views

Finding zero of nonlinear simultaneous equations [closed]

I'm trying to find the zero of nonlinear simultaneous equations defined in myfun1 and myfun2: ...
8
votes
2answers
128 views

Numerical solve question

Why does this work? Solve[5 Tan[t] + 9 == 0 && 0 <= t < 2 Pi , t] {{t -> π - ArcTan[9/5]}, {t -> 2 π - ArcTan[9/5]}} But this doesn't. ...
4
votes
0answers
211 views

Strange behaviour of NotElement in Reduce

Bug introduced in 8.0 or earlier and persisting through 10.4 or later Confirmed, as bug, by WRI: [CASE:3527549] I have observed curious behaviour on domains supplied to ...
1
vote
1answer
96 views

Solve differential equations with an initial condition in the form of a limit as $t\rightarrow \infty$

I want to solve the following differential equation with the initial condition This is known as the Bunch-Davies vacuum, and the above are equations (4.1) and (3.37) from this paper Here is ...
4
votes
1answer
217 views

How to speed up calculation of this equation (FindRoot)

I have come up with the following functions, and I need to calculate a value, in order to have a condition valid. In my problem, all data are given, and I need to calculate variable l. I am using ...
15
votes
3answers
525 views

Solving the magic backyard puzzle with MMA

I was trying to solve this puzzle using mma It looks like the generalization of the magic square. Anyway here my attempt:- There are four columns $(x,y,z,w)$ and nine rowa which are denoted by the ...
5
votes
1answer
285 views

A problem about Steffensen method

Two days ago,I asked a question about bisection algorithm. Thanks for Michael E2 giving me a good solution My algorithm 1, I use the bisection algorithm to generate a initial value that contain a ...
2
votes
2answers
76 views

Integral equation solving

So there is this equation that I have to numerically solve for T: Q/(3nRT) = f(T/300) - f(T/77) Here Q = 920.364, n = 0.24, R = 8.314 while f is defined as the ...
1
vote
1answer
98 views

Computing the coefficients for Gaussian integral

I wrote a small script to find the Gaussian integral points and weights: ...
1
vote
0answers
62 views

DSolve throws an error about Solve and returns unevaluated [duplicate]

I evaluate: DSolve[{2*y[x] + y'[x]^2 + a*x^b == 0}, y[x], x] During evaluation of In[26]:= Solve::ifun: Inverse functions are being used by Solve, so some ...
2
votes
2answers
194 views

Quadratic Equations $\bmod p^k$

As part of a larger program, I need to solve $A x^2+B x+C \equiv 0 \pmod {p^k}$ for prime $p$. Right now I'm doing this by calling ...
2
votes
1answer
76 views

Can not Solve FinancialDerivative for volatility

Although Solve can solve FinancialBond for an input parameter (e.g. par) given the price of a bond: ...
0
votes
1answer
44 views
5
votes
2answers
102 views

Rewriting expression in terms of factor

I have two expressions: expr = (a - R)^2 (a + 2 R)/(2 R^3); factor = 1 - a^2/R^2; I would like to write expr in terms of ...
-1
votes
2answers
79 views
0
votes
0answers
27 views

Solve does not give solutions to all variables [duplicate]

I have a beam with $n$ points and I have to find a numerical solution of the axial force using Finite difference method Here is my code ...
1
vote
1answer
76 views

DSolve to make the path of a ball in a rotating turntable

I have two equations from a analisys of the following situation. A ball starts to move from the center of a Turntable (rotating disk). I tried to solve these equations on Mathematica but the ...
3
votes
4answers
173 views

Find the minimum positive-integer value which meet the requirement

If the equation is Mod[515 Sum[10^(3 d), {d, 0, n}], 53] == 0 Then I can get the minimum positive-integer value of n. ...
4
votes
5answers
377 views

Solve for exponents

I have this problem that I"m trying to work out: Here's my attemp: me = 0.51109991 mp = 938.2723 mpe = mp/me Solve[(2^n)*(3^mm)*(\[Pi]^p) == mpe, {n, mm, p}] ...