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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2answers
88 views

Closed form solution equations involving finite sums

I am a beginner in Mathematica, so take this into account. I could not find anything similar in the internet so far. I am trying to find a closed form solution for ...
2
votes
1answer
47 views

FindInstance skips solutions

I have an equation to compute the bit-error rate of a binary symmetric channel: $$P_{err}(n,p) = \sum_{k = \frac{n-1}{2} + 1}^n\binom n k p^k(1-p)^{n-k}$$ I then want to find the smallest ...
0
votes
0answers
93 views

Solving general system of equations

I want to find the closed form solution to a general system of equations. The number of equations and variables is C. How do I specify the system of equations? If ...
0
votes
1answer
123 views

Help on using Solve

I tried to use Solve to solve a set of nonlinear equations and got this error: Solve was unable to solve the system with inexact coefficients or the system ...
1
vote
1answer
69 views

Double arrow in the outcome

Does anyone know how do I get rid of one of the double part at the start of the outcome rh-> rh-> ...
4
votes
1answer
88 views

How to equate coefficient of two polynomials? [closed]

Given two polynomials, How can I equate coefficients of them in Mathematica? For instance a + b x + (c+d) x^2 + (e+f)x^3 == 0
2
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1answer
122 views

How to handle a special Neumann-like boundary condition in NDSolve?

How to solve the following nonlinear ODE with two algebraic equations and one boundary condition? ...
0
votes
0answers
59 views

Is this problem parametrically solvable or it can just be solved for specific $\sigma$ and $\theta$?

In order to solve This problem: What is the maximum value of coefficient fv with the constraint that the matrix is positive semi-definite?, I have used the following code (Determinant is computed by ...
0
votes
1answer
54 views

Multiple stopping constraints in NDSolve

I need to numerically solve several differential equations, with several constraints, like this : ...
0
votes
1answer
88 views

How to solve the following GR PDE?

Someone could help me for solving the following GR PDE? (this code do not work yet) ...
0
votes
1answer
52 views

Using Solve with Mod [closed]

I'm new to Mathematica, and it seems like what I'm doing should be a simple operation, but I can't seem to get it to work, or return the right result. I'm assuming I'm doing something fundamentally ...
3
votes
0answers
73 views

Low accuracy while solving a multi-variable equation numerically

My question is as following: I was trying to make a function Vs2[r] with two parameters fit a set of conditions. Vs2[r]: ...
2
votes
1answer
70 views

How to get the analytical solution of this equation set

There is a equation set: {2 x^2 + 49 - 7 x - 2 x Sqrt[x^2 + 49 - 7 x] Cos[rad] == (7 - x)^2, 2 x^2 + 49 - 7 x - 2 x Sqrt[x^2 + 49 - 7 x] Cos[rad + Pi/3] == 49} ...
0
votes
1answer
72 views

what do those signs #1, #1^2, #1^3, & mean here? [duplicate]

I have read common pitfalls page and the documentation page but I still don't understand what do those signs mean here? ...
0
votes
1answer
53 views

How to represent one variable in terms of others in a system of equations? [closed]

I have an pretty complex equation set But when I clicked Ctrl+Enter (a.k.a Evaluate Cell), nothing happened. What should I do?
3
votes
1answer
65 views

Havin the problem with solving a nonlinear overdetermined system of equations

I am having a problem to solve a nonlinear overdetermined system of equations. According to one of the previous posts, I tried NMinimize, but it didn’t work. Shall ...
0
votes
0answers
84 views

FindInstance—why doesn't it work with my expression?

I want to find arbitrary solution of a system of equations: ...
0
votes
1answer
66 views

Computing quadrature points on triangle

According to http://math2.uncc.edu/~shaodeng/TEACHING/math5172/Lectures/Lect_15.PDF page 7, it is possible to compute coordinate of quadrature points by using the script ...
0
votes
0answers
19 views

Solving a simple ODE [duplicate]

I am trying to solve $y(x)' = \sqrt{y(x)}$ with initial condition $y(0)=0$ for $x\in \mathbb{R}$. I have tried this: DSolve[{y'[x] == Sqrt[y[x]], y[0] == 0}, y[x], x] but this gives {{y[x] -> ...
1
vote
0answers
83 views

Using functions in Solve [closed]

i wanted to calculate the real roots of a function. To my knowledge the function i defined has no real roots, so i expected an emptyset, but instead i got some Root[...#..] answers by Mathematica. ...
0
votes
1answer
55 views

$4$-d system of second order PDEs

I have a $4$-dimensional nonlinear system of second order PDEs with periodic boundary conditions. Let $y(t,x)=(y_1(t,x),...,y_4(t,x))$ with $t \in \mathbb{R}$ and $x \in [0,1]$ then the system is ...
4
votes
0answers
210 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 ...
2
votes
1answer
100 views

Issue with NSolve for solving six equation and six unkown [closed]

I am trying to solve the following six equations and six unknown but It takes me one hour then the program stops. Would you please give some help. I am a beginner. $eqe1=0.000466667 \left(A_2 \cosh ...
0
votes
1answer
48 views

Simple grouping equations [closed]

I'm new in the Mathematica world. A very basic question. I have been using the command Eliminate on a set of equations as follow: ...
0
votes
0answers
35 views

Using Solve with NIntegrate [duplicate]

I have a function defined as a numerical integral of a parameter. When I try to solve for the parameter Mathematica complains that the integrand has evaluated to a non-numerical value (which makes ...
0
votes
1answer
80 views

How can I calculate the root of any order of power series

How can I calculate the root of any order of power series with Mathematica. Here I insert every quantity by hand. But I want to give a, ...
0
votes
1answer
56 views

Eliminate variable on multiple equations [closed]

I'm pretty new with Mathematica. I have to perform a really simple operation, but I'm really struggling with that. I have a set of 4 equations, for example (they can also be more complex): $ AA = 2 ...
0
votes
2answers
64 views

How to find the value of a variable using solution of Simultaneous equations? [closed]

I have to find the value of p where p=a1*x+b2*y; using the solution of the equation ...
2
votes
1answer
100 views

How do I find the analytical roots of this polynomial? [closed]

I want to find the analytical roots of this polynomial - x - a^3*x*(a^2*x*(a*x*(x - 1) + 1)*(x - 1) + 1)*(a*x*(x - 1) + 1)*(x - 1) ...
0
votes
1answer
37 views

Transform system of equations while leaving solution set invariant?

Consider the example system of equations syst==res where syst={x + 2 y + 3 x y, 1 + 4 x + y}; res={0 , 0}; Solving for the ...
1
vote
0answers
47 views

Solve Two Functions In Three Variables and use ContourPlot [closed]

I am solving this system in mathematica ...
0
votes
1answer
39 views

Simplify doesn't simplify multiple conditions from Reduce

Consider the following simple example where I try to solve an equation and then apply a bounded interval to find the right result out of an infinite amount of solutions: ...
2
votes
1answer
95 views

FindRoot of interpolating function from NDSolve

I am having issues finding the root of an interpolating function obtained from NDSolve. For example: ...
2
votes
2answers
229 views

Simultaneous equations—classify the solution set as finite, infinite, or none [duplicate]

How do I find the values of $b$ and $c$ for the equations $x + 5 y = 4$ and $2 x + by = c$ with a unique solution, an infinite set of solutions and no solutions with Mathematica?
1
vote
1answer
54 views

Solving a simple trigonometric equation in a range

I would like to solve a simple trigonometric equation, for example $\sin\theta=\frac{1}{2},$ but Solve gives the single solution obtained by using the inverse ...
0
votes
2answers
102 views

Finding all complex polynomial roots in a specified range efficiently

I need to find the roots of a rational polynomial that are near i. In the following code, I try that two different ways. First, I use a constraint to only find roots in the right region. Second, I ...
1
vote
1answer
95 views

How do I plot this (x^3 - 2*x)^Ln[x]? [closed]

y=(x^3 - 2*x)^Ln[x] I'm totally clueless. I tried with y=e^(Ln[x] Ln[-2 x + x^3]) by Ln-ing on both sides but there is ...
1
vote
0answers
49 views

Strange behavior when solving absolute value equations

Try this: Solve[Abs[x/2 - 1/3] == 1, x] Produces this answer: (* {{x -> -(4/3)}, {x -> 8/3}} *) Now try this: ...
0
votes
0answers
63 views

Help numerically solve this non-linear PDE with singularity

I have trouble finding a numerical solution to the partial differential equation below. It seems to be a singularity in the solution somewhere, so I searched online and found that it is suggested to ...
14
votes
3answers
404 views

Is there any predictor-corrector method in Mathematica for solving nonlinear system of algebraic equations?

The FindRoot Function in Matheatica can easily be used to solve systems of nonlinear algebraic equations. But, I want to solve a system of nonlinear equations with variations of some parameters. ...
1
vote
1answer
81 views

Solving equations with subscripted variables

A student of mine tried: Solve[1/R == 1/Subscript[R, 1] + 1/Subscript[R, 2], R] which did not work. We then tried: ...
0
votes
0answers
29 views

Quickly Solving a High-Order Root System of Equations of Arbitrary Form

I have the following system of equations that involve some rather complicated exponents: $$ \left\{\frac{\mathit{a} \sigma ^{41/34}}{\mathit{m}^{8/119} ...
1
vote
1answer
70 views

I can not solve this equation for recurrence [closed]

Use RSolver to solve RSolve [{f [n + 1] == f [n] + 2 n + 1, f [1] == -3}, f [n], n] but I do not get solution Edit my solution
0
votes
0answers
46 views

How to get x = 1.234 from {x -> 1.234}? [duplicate]

I'm a complete beginner in Mathematica (started a couple of days ago). I've solved a function using "Solve" and the result is this one: Out[1] = {x -> 0.000942939} How do I get the 0.000942939 ...
0
votes
0answers
75 views

Solving numerically a system of equations using different methods

I will use, as an example, the simple Henon-Heiles potential ...
1
vote
2answers
97 views

Bessel-like equation problem with NDSolve

I am trying to solve the following nonlinear ODE, but Mathematica takes forever to give a result. Any idea why? ...
9
votes
2answers
195 views

NSolve finds real-valued results in version 9, but not in version 10

UPDATE Reals also was used in the code. Actually, I tried the following simple piece of code. ...
1
vote
1answer
61 views

how to replace one calaculation result to another one in a loop?

I am doing the calculation in a loop. I gain a digit for rzin in ...