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

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1answer
55 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} ...
2
votes
1answer
90 views

Issue with NSolve for solving six equation and six unkown [on hold]

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 ...
2
votes
1answer
113 views

Approximating Magnitude of Solutions

I was recently lecturing on the hierarchy of functions in a calculus class. Discussing the fact that eventually any exponential growth function will overcome any polynomial. As an example, I tried ...
2
votes
1answer
92 views

Exclusions found but Solve and Reduce don't find exclusions

I have the following from Stan Wagons Mathematica in Action. ...
2
votes
1answer
148 views

How to Solve[] for rational constants?

I am trying to solve a system equations for rational, constant coefficients: ...
2
votes
2answers
122 views

Only one root at specific interval

I need a help to find k here: $f(x)=-k^x + x^2$ It is not too simple. I have interest to find the single value of "k" where, inside interval {x,2,3}, the function have only one value to x when f(x) ...
2
votes
1answer
240 views

Structure analysis based on direct stiffness method. Solve taking too much time

The program generates a very large matrix based on some input from the user. The matrix is symmetric and called generalstifnessmatrix. It also generates 2 other lists(displacement and forces list) ...
2
votes
1answer
417 views

Solving a system of nonlinear equations

The bellow set of equations has two answer sets for (α1, α2, α3, β1, β2, β3) respectively as following: (3, 1, 3, 1, 1, 1) & (3, 0.75, 3, 0.5, -1, 0.5) ...
2
votes
2answers
167 views

How to obtain a function from a implicit equation?

I have (60 - r/2) (70 - ca - r/2) - (60 - r/2 - ca + (4/25) (70 - r/2 - ca))*(70 - r/2)==0 Reduce[%, {ca}] But How could I obtain directly a function as ca[r_] ...
2
votes
2answers
336 views

NSolve for high degree univariate polynomials

I am trying to solve a high degree univariate polynomial using Mathematica's NSolve command. But when I plug the solutions generated by Mathematica back to the equations, the equations are massive ...
2
votes
1answer
225 views

How to solve this numerically?

May I ask what is the best way to evaluate ...
2
votes
1answer
1k views

Nonlinear least squares

I have a typical nonlinear least square problem and it seems very similar to the example provided in the section on parameter fitting at the Wolfram website. Unfortunately I always get some error ...
2
votes
2answers
110 views

Puzzling behavior produced by Exists

I need to simplify a set of solutions of a system, say for example: ...
2
votes
1answer
2k views

Solve matrix equation A*X=X*B using LeastSquares

I want to solve matrix equation A*X=X*B using LeastSquares method, but it is suited for equation like A*X=B. All matrices are 3x3 ...
2
votes
2answers
115 views

Solving two non-linear equations with two unknowns [duplicate]

I'm a beginner in Mathematica. I'm trying to solve : ...
2
votes
1answer
62 views

RootReduce-Part of Solve

I have given the following expression in $M$ and $z$: \begin{equation} a = \frac{-4 M^2+M (-3 z-5)+\frac{1.1875 z}{\sqrt{\frac{0.015625 z}{M+1}-1.5625} \sqrt{\frac{0.765625 ...
2
votes
1answer
145 views

Solve overdetermined set using Mathematica?

As shown below, this is a overdetermined system. Could you teach me how to find the optimized solution in Mathematica? I know it could be solved by the method of least square, but how to realize it in ...
2
votes
2answers
174 views

Solve a symbolic underdetermined Linear System

Dear StackExchange Community, I'm trying to solve an indeterminate linear system of equations, with $n+1$ variables and $n$ equations; therefore, I need to express all $n$ other variables a function ...
2
votes
3answers
269 views

Solve a transcendental equation in Mathemathica

I believe it is called a "transcendental equation", and I would like to find the best possible sollution. I tried to use Solve: ...
2
votes
2answers
122 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.
2
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1answer
162 views

How can I find all solutions of a complicated expression in a desired interval with Mathematica?

I have an expression which is a combination of Bessel functions: ...
2
votes
2answers
138 views

A peculiar behavior of NSolve[]

NSolve[Power[x + 1, x + 1] - Power[x, x + 2] == 0, x, Reals] returns: {{x -> 3.14104}} Great. However, ...
2
votes
4answers
204 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 ...
2
votes
2answers
362 views

Solve ODE in State-space form

Is it possible to solve an ODE in state-space form in mathematica? Such as x'[t]=A.x[t] I attempted ...
2
votes
3answers
128 views

MapAt a function at specific positions

I'm trying to solve for $p3$ in 3p3-5 = p1 + p2 at positions where p1*p2 == 0: ...
2
votes
2answers
329 views

Given a system of inequalities, how to make Solve find out that two variables should be equal?

Given two boolean variables x1 and x2 (in the sense that they are in the range [0,1]), if I try to solve the following equation system with Solve: ...
2
votes
2answers
299 views

How do I feed data points into an equation to solve NUMERICALLY?

I start with this equation and solve it numerically for $z(x,y)$ in the range $1 < x < 5$ and $1 < y < 5$: $$ \frac{3}{xyz} - 2x - 3y - 5z = 0 $$ Then using the data points of $z$ above, ...
2
votes
3answers
156 views

Solve works with numbers but not number stored in variable

I have the code: ...
2
votes
1answer
191 views

Solving problems with the floor function

I've got the following problem: If I want to calculate the following equation, ...
2
votes
3answers
756 views

Solve the system of equalities and inequalities

I have a system of expressions, in which each expression is an equality or inequality expression of the following form: Var = Var1 + Var2 Var $\odot$ number Var $\odot$ Var1 $\odot$ = $\leq | \geq | ...
2
votes
1answer
481 views

Solving an equation involving a determinant

I have a matrix which doesn't include numerical values. There are four variables in it. It is defined by ...
2
votes
1answer
544 views

How to solve simultaneous equations faster with Compile?

I have large 6x6 matrix Uwhich is a multiplication of 15 rotational matrix. All of the elements are Sin\[theta] and ...
2
votes
2answers
3k views

Root finding in Mathematica

I am new to Mathematica. I have used the WolframAlpha online calculator to find roots of equations (listed under the heading Root in the output generated in ...
2
votes
1answer
112 views

Problem with implementing Regula Falsi [closed]

I checked the "Questions that may already have your answer" and didn't really find what I need. It's actually pretty basic. I want to solve an equation manually with Regula Falsi. I dont need a ...
2
votes
1answer
61 views

Plot the result of Solve for multivalued solution

I would like to plot the (most likely) multi-valued solution to an equation, as I vary one of the parameters. Here's my approach: ...
2
votes
1answer
293 views

Why does Wolfram Alpha not return a solution to this problem involving Floor[]? [closed]

Wolfram Alpha did not find the solution $$x=\frac{8}{7} , y=7$$ to the equations below. Why? What can be done to expect more accurate results from Wolfram Alpha, in similar cases?
2
votes
2answers
73 views

Return approximation error with FindRoot

I am solving a large system of equations. I would like to know to which extent the the solution that FindRoot returns to me is accurate: ...
2
votes
1answer
87 views

Solve for a range of values

I am trying to solve the following eqn for Tco. The ultimate goal is to Plot Tco for zb values from 0 to 12. ...
2
votes
1answer
204 views

Solving a transcendental equation

I want to solve the a transcendental equation, e.g. NSolve[-(1-x)*Log[1-x] - x*Log[x] == 0.5, x] Mathematica is not able to solve, wheres WolframAlpha -- is able ...
2
votes
2answers
117 views

Series expression of a Root object

I was wondering if it is possible to get Mathematica to return a series approximation of a Root object. Example: I want a series representation of x in terms of ...
2
votes
2answers
521 views

Find roots of a function involving Bessel functions

I'm trying to find the roots of a function involving Bessel functions. Here is my code ...
2
votes
2answers
185 views

Extract data from NDSolveValue result

Okay this is a very newbie question. I have coded a sample problem that solves the heat diffusion equation on an annulus. Here's what I have: ...
2
votes
1answer
336 views

why doesn't NSolve find all the solutions that Solve finds?

Define d[p1_, p2_] := (p1 - p2).(p1 - p2) to be the square of the distance between two points. I am trying to solve equations like: ...
2
votes
3answers
395 views

Is there a way to specify custom domains?

I want to solve for all solutions to the system of equations $a_1 a_2 a_3 b_4 + a_1 a_2 b_3 + a_1 b_2 + b_1 = 0$ and $a_1 a_2 a_3 a_4 = 1$ where the $a_i$'s and $b_i$'s take on values from $\{-1,1\}$. ...
2
votes
1answer
558 views

How do I get all possible solutions in an underdetermined system? [duplicate]

I have two problems which I'd like to solve with Mathematica. If I have a system of two equations with three unknowns, how can I get to list all possible solutions for the unknowns? Here is what I ...
2
votes
2answers
161 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) ...
2
votes
2answers
209 views
2
votes
1answer
143 views

Decomposing a diagonal positive real matrix

I would like to 'decompose' a diagonal positive real matrix $E$ of rank $D$ onto $\sum_{i=1}^{D}c(i)N^i$: $$E = \left( \begin{array}{ccc} 0 & & & \\ & a & & \\ ...
2
votes
1answer
103 views

Possible to Solve a LocationEquivalenceTest?

I have 5 groups, each containing around 20 elements. These elements are all dependent on x. For example: Set1 = {1.5x + 1, 2x + 0.5, 1 x + 1, ...} etc. Now, I want ...
2
votes
1answer
732 views

Distance between 3D curves

I would like to determine the distance bewteen two representations of the Lorenz Attractor. I have two 3D representations for different initial conditions and I want to calculate the distance between ...