Tagged Questions
3
votes
0answers
115 views
FindRoot gives a wrong solution which obviously should not be there
I got stuck on FindRoot and I didn't see any similar problem posted, so let me explain what I am trying to do and what problem I meet here.
I try to find roots of a particular function, which in the ...
3
votes
1answer
75 views
Find point at which equation stops having roots (if it exists)
I am interested in the roots of this function:
f[M_, b_] := 1 - (2 M Gamma[2, 0, (1/M + b M)/Sqrt[b]])/(1/M + b M)
for fixed values of b. In particular I want ...
0
votes
1answer
79 views
How to guess initial complex value for FindRoot
I have to solve a transcendental equation for a parameter, say $\beta$. Now, the $\beta$ has a range from $ik$ to $k$ where $i$ is the usual imaginary root $\sqrt{-1}$ and $k$ is a real number. ...
3
votes
2answers
134 views
4
votes
1answer
177 views
NDSolve does not respond
For some sets of constants, NDSolve gives me true solutions, but when I try for example, T = 1/(2*2200), Mathematica does not respond. What can I do? The code below ...
1
vote
0answers
72 views
Why is FindRoot initial value far from the specified one?
I am trying to numerically find the root of a function that looks a bit like: 1/x - (SchurDecomposition[A[x]][[2]])[[1]], where ...
2
votes
1answer
155 views
How to solve equations self-consistently
I want to solve the following equation self-consistently. So,
H.u = e.u
{{1, d}, {d, 1}}.{u1, u2} = e.{u1, u2}
I guess an initial value for ...
4
votes
2answers
138 views
Finding all/most roots of a discontinuous function more consistently?
I have the equation:
f[x_]:=α Tan[α*a] - Sqrt[c - α^2]
and ideally I want to find all of its positive zeros, given a and c, with variable alpha. The problem is ...
1
vote
1answer
345 views
Forcing FindRoot to return only real solutions
FindRoot documentation reports that if the Equation and the initial point are reals, the solutions are searched in the real domain.
However, in the following case I ...
4
votes
2answers
174 views
How to solve this trigonometric system of equations numerically?
How can the following trigonometric system of equations be solved numerically?
...
2
votes
0answers
173 views
Numerically/Analytically Solving a System of Equations
I have $6$ functions $f_i(x,y,z)$, $(i = 1, \ldots, 6)$ in three variables $x,y,z$, and I would like to find a simultaneous instance of these variables, say $(x_0, y_0, z_0)$, such that $f_i(x_0, y_0, ...
3
votes
0answers
256 views
How can I solve this complicated custom function numerically?
I have a complicated function that calculates the total value of payments from an account into which deposits are made annually. I'd like to solve the function for a growth rate numerically, but ...
3
votes
3answers
265 views
How can I solve Tan[t] - t == F[x] for t as a function of x?
How can I solve the equation Tan[t] - t = Ax, where A is a constant for t[x]?
I know that ...
0
votes
1answer
143 views
0
votes
1answer
115 views
Industrial Level Applications. Recipe for mixed notation of equations set
I am working with large (linear) equations set within Mathematica in numerical notation. For example, set from 4056 eq. is solved for a second, no more. There is no doubt, result is great. But even ...
0
votes
1answer
495 views
Tricks for solving (lots of) coupled nonlinear equations numerically?
I have a system of 6 non-linear (quadratic) coupled equations with 6 complex unknowns
\begin{align*}
|x_1|^2 + |x_2|^2 + |x_3|^2 &= a\\
x_1 x_4^* + x_3 x_5^* &= b + c i\\
x_1 ...
0
votes
0answers
83 views
FindRoot is only passing two variables
When I run the code:
q0 = FindRoot[findarea[ch, rh, ah, lineh, intersecth, q][[1 ;; 2]] == ah[[1 ;; 2]]*r3^2,
{q, q0}][[1, 2]];
...
8
votes
1answer
377 views
How do I find all the solutions of three simultaneous equations within a given box?
Sometimes, one needs to find all the solutions of three simultaneous nonlinear equations in three unknowns
$$\begin{align*}f(x,y,z)&=0\\g(x,y,z)&=0\\h(x,y,z)&=0\end{align*}$$
within a ...
2
votes
1answer
227 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 ...
1
vote
3answers
282 views
equation solving problems
I have some equation:
$$
veq=-2-lr-l^2r+2(r+ir^3\omega) v' + (-2+r)r^2v'^2 + (-2+r) r^2 v''==0
$$
or in Mathematica form:
...
3
votes
2answers
426 views
Numerically Solving two dependent Transcendental Equations
I need to solve a system similar to the following (Except it is quite large. Solving this ought to do the job):
$$ \tan[2f(t)] = 1+ t^2\ $$
and
$ f(t) $ is $ k $, such that$$ \tan[2kt]-(1+k^2) = 0\ ...
0
votes
1answer
396 views
how to solve an implicit integral equation? (iterate to a functional fixed point?) [closed]
I reduced a (special case) of my problem to the following code. Even though in this special case all related functions are analytical, DSolve is not the tool for this, though I am indeed looking for a ...
0
votes
1answer
88 views
Numerical rule evaluation -> {True, False} to deviation of target equation
I solve some equations numerically with FindRoot[] returning a quadruple {1,2,3,4}.
Because the solver sometimes do not find any roots depending on parameterization of these equations I select only ...
10
votes
6answers
2k 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 ...
6
votes
2answers
364 views
Number of iterations in NSolve
In Excel's solver, one can define how many iterations are to be done, to one's liking.
I am wondering if this is possible to do with NSolve in Mathematica?
Code
...
6
votes
1answer
457 views
Handling failed FindRoot calls
I want to handle FindRoot calls which did not converge (e.g "thrown" error message FindRoot::cvmit)
...
8
votes
2answers
519 views
RootSearch for complex or multiple equations
First the background. I'm trying to solve for the roots of a rather messy complex equation. This is not the exact equation, but it's a decent (simpler) stand in:
...
7
votes
1answer
340 views
Using Mathematica to help to determine the consistency of and numerically solve systems of non-linear equations
The formal problem
The question I am about to ask is applicable to many scientific and engineering problems. In short, I am bout to ask for pointers and practical advice for Mathematica beginners who ...
31
votes
7answers
888 views
Updating Wagon's FindAllCrossings2D[] function
Stan Wagon's Mathematica in Action (second edition; I haven't read the third edition and I'm hoping to eventually see it), demonstrates a nifty function called ...
