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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1answer
57 views

How to extract a solution

Is there any way to get the actual number from this? NSolve[x^2 - 5 y^2 == 1, {x, y}, Integers][[1]][[1]] instead of ...
13
votes
4answers
635 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 ...
0
votes
0answers
38 views

NSolve can not handle a PolyGamma equation

I would like to solve the following equations numerically: ...
1
vote
0answers
88 views
11
votes
2answers
11k views

Figuring when the minute and hour hand coincide on a clock

I would like to list all possible times in a 12-hour period, where the hour hand overlaps the minute hand completely. This is really a question about three distinct things - to be done in Mathematica ...
-1
votes
1answer
95 views

How to get a 3D plot of from the the solutions of function [closed]

I have the following equation: (1 - x)^2 + T^2/((f[x] - L)*(f[x] - L - 2*T))*(P/(N-R+S)) == 0 f[x] = (x*r*(T + L) - T)/((x*r) - 1) ...
0
votes
1answer
96 views

How to put a condition in 3d plotting

I have the following plotting question: First I want to have 3D plot of Alpha respect to different values of p and l when we ...
0
votes
2answers
131 views

How to write Newton-Raphson module and return a value?

I am writing a code which solve nonlinear algebraic systems via Newton-Raphson algorithm. I want to make a Newton Module with another file and use the Module in my test file, but i didn't achieve it. ...
0
votes
1answer
62 views

Plotting results of a NSolve problem

I am calculating, numerically, the zeros of a determinant. a1 and a2 are constants, q is a parameter. I would like to vary q and find the roots w as a function of q and plot roots w vs. q. All ...
1
vote
1answer
76 views

NSolve on bounded domain

I don't expect NSolve[] to be able to obtain all solutions in generalfor example. In principle there should be an algorithm that finds all solution to $f(x)=0$ for ...
2
votes
3answers
98 views

How to merge permutations obtained from Solve on multiple variables?

When I compute the following expression to find integer solutions of the equation (x^2 + y^2 + z^2 == 14^2) ...
0
votes
1answer
142 views

Plotting an extremly large output

I'm trying to plot the solutions of this determinant: ...
10
votes
3answers
359 views

FindInstance with a Diophantine equation seems to go on forever

I tried to find a non-trivial integer solution to the equation $$2012^2=a^2+b^2+c^2+d^2+e^2$$ with Mathematica but the computation takes minutes; I might be doing something wrong. ...
3
votes
3answers
169 views

How to solve the equation $A \sin x + B \cos x = 0$ for all $x$?

I have the equation: $A \sin x + B \cos[x] = 0$ that should be satisfied for all the $x$. Of course, the solution is obvious: $A=B=0$, but I need Mathematica to resolve it automatically because this ...
1
vote
1answer
184 views

NSolve fails to solve a nonlinear equation

Mathematica can not solve this: g = 9.82; ω = 0.5; h = 5; y0 = 1; v = 0; τ = 0; NSolve[h + v t - (g t^2)/2 == y0 Sin[ω t], t]; The error code is: ...
2
votes
2answers
81 views

How do I get all the roots within a certain range for an equation? [duplicate]

I wish to find ALL the roots of the following equation $ x \tan(ax) - c = 0$ within a range, where a and c are constants I control. I've been using ...
0
votes
1answer
70 views

How to solve this equation? or get the numbers of solutions of the function?

I have a function like this.. $$ f[k]=\int_0^\infty Exp[-ax]x(Cos[bx])^{2}BesslJ[0,kx]dx $$ I want to know how many local maximuns this function has.. So I try to get the derivative of f[k] $$ ...
1
vote
1answer
76 views

How to solve these equations by Mathematica?

l tried it with Solve,DSolve and NDSolve functions,but all failed.Should l simplify the equations in the papers or use other mathematica functions.Thanks~
1
vote
2answers
62 views

Solutions to multivariate equation

Is there any way to get Mathematica to give a set of solutions (pairs of x and y that are integers) to an equation with multiple variables? Something like: ...
0
votes
0answers
79 views

Solving a system of equations involving partial derivatives for a wave

Before saying anything about the problem, I have checked "How to solve a system of partial differential equations?" yet it does not actually answers my question, as I have a 10x10 matrix to work on. ...
1
vote
0answers
44 views

Equation solving: Solve returns a periodic solution

I have a very simple trigonometric equation, that I've been trying to solve for a variable for a few hours now: (I couldn't find how to correctly format this) ...
0
votes
1answer
65 views

Why does this work with Wolfram|Alpha but not Mathematica? [closed]

I ran into this while doing some work today: It's the exact same syntax - and I expected that Mathematica would be more likely to be able to solve it, since oftentimes Wolfram|Alpha doesn't have ...
0
votes
0answers
31 views

Initial values/parameters in equation system of dimension 32

This is a system of equations of dimension 32, that describes an economic system. I want to find a set of parameters and initial values in which the system can be solved, and solve the system of ...
1
vote
1answer
56 views

Characterising the set of parameters that satisfy a system of non-linear equations

I am looking for a solution to the following problem and could not find an answer so far. I have a quintic equation, $f(x;a,b,c,\cdots)-x=0$, where $x$ is the variable with respect to which I need the ...
1
vote
1answer
188 views

solve recursion equation with condition

How can I find $f(x)$ in terms of $x$ in the following equation? $ -k\, x \,f(x) + k \, (x + 1)\, f(x + 1) - r \, f(x) + r\, f(x - 1) =0$ $r$ and $k$ are constants and $f(x)$ should satisfy: ...
0
votes
2answers
63 views

Very slow solve and problem when solving in a nested for loop

I am using a nested for loop to solve a system of equation for {a, ga} for 2 varying parameters: here it's rm and sig. ...
0
votes
0answers
55 views

Enormous and unclear output when using Solve

After running for about 30 minutes the program yields the below-given unclear output (of course I didn't copy the whole output, only a small part of it). So it explicitely gives 3 possible solutions ...
2
votes
1answer
84 views

How to obtain numerical answer for equation containing integration

Could some one tell me how to obtain numerical value of $a$ and $b$ from equations below: $$\frac{1+exp(b)}{1+exp(0.9a+b)}=0.95$$ $$\int_{0}^{\infty} \frac{1+exp(b)}{1+exp(a x+b)}=1$$
0
votes
0answers
55 views

Selecting values over lists for discrete inputs in NDSolve

I'm currently trying to simulate a step response in a simple tank system with NDSolve. I would like it to start at say time 2 (the precise time is not important). ...
0
votes
1answer
78 views

Solving a complicated system

Could anybody please make a suggestion how can I implement this program which attempts to solve $2$ dimensional complex system of equations? My computer is not able to solve... After 3 hours the ...
3
votes
3answers
998 views

Using DSolve to solve for x[t,parameter]

I'm trying to solve an ODE with two independent variables (a cannon firing from a cliff incorporating wind resistance dependent on velocity). I've tried the following for the x-component: ...
2
votes
0answers
55 views

NDSolve is running an extremely long time: how can I save the existing data?

I am trying to solve a PDE by the following code. It takes 1 hour or so to reach t=25.72 but about 20 hours to reach t=25.72404031638060174049337306126853310997. Actually, the time step is extremely ...
2
votes
0answers
117 views

Proving large inequality in 6 variables

I have arrived at a very large inequality in 6 variables that I would like to prove is true. The command I have tried is the following: ...
0
votes
2answers
93 views

Obtaining the relations of variables using diagonal matrices

I know this is too an elementary question, but I am a pathetic newbie in mathematica and I cannot find any answer by googling. What I want is obtaining some relations of unknown variables using their ...
3
votes
1answer
137 views

Fick's Law over Implicit Regions

I'm trying to solve 2D Fick's law of diffusion from the boundaries of a triangle (future shapes will include more complex implicit regions). I'm able to model diffusion without time in complex ...
4
votes
2answers
138 views

How can I get all solutions of a system of equations with Reduce?

The post What is the difference between Reduce and Solve? discusses the difference between Reduce and Solve. Now, with the ...
0
votes
1answer
123 views

How do I write nested for-loops?

Looking through the reference.wolfram, I couldn't see an example of how to write a multiple line "for" loop in Mathematica. I need to nest many for-loops in such a way I can do many things in the ...
0
votes
1answer
70 views

Weird behavior when solving a simple physics problem

I have the following code in Mathematica that represents two balls being thrown, one with a velocity v10 (6 in this case) and another ball thrown with a velocity v20 (its just dropped) one second ...
0
votes
2answers
72 views

How to exract the roots from “Roots”? [duplicate]

Given how the output looks like, as in a set of "==" assignments, is it possible to extract specific roots from the output of, http://reference.wolfram.com/language/ref/Roots.html ? And then do a ...
1
vote
1answer
122 views

Runge-Kutta Butcher tables

I like to have the Butcher's table for Explicit (or implicit as well) Runge-Kutta method of a fixed order. I do not understand reading ...
3
votes
1answer
116 views

How to reduce a quartic form to a quadratic form with equal roots

Preface: To clear the theoretical background this question is cross-posted on math.stackexchange here. I have a polynomial in $n$ variables of the form ...
3
votes
1answer
125 views

Solving Non-linear System of Equations

I need to get a symbolic solution to a system of non-linear equations (equation 8 is non-linear), but Mathematica is running for ever and gives no answer. Is there another way to get the solution? My ...
4
votes
1answer
133 views

Solving 2-D Mechanical Systems

I'm trying to use Mathematica to solve a particular 2-d mechanical system. The system comes from "DESIGN AND OPTIMIZATION OF AN EIGHT-BAR LEGGED WALKING MECHANISM IMITATING A KINETIC SCULPTURE, “WIND ...
1
vote
2answers
137 views

Intersection with FindInstance

How to find individual root parameters pair ( t, T) to find curve intersections using FindInstance? Hopefully it would output two, instead of 6 pairs in the following: ...
0
votes
2answers
80 views

Solving a system of two equations

I have a system of two equations with the variables T and X that I tried to solve: ...
-3
votes
1answer
78 views

How to make X and Y = Z? [closed]

Hello I have a big question, maybe it's extremely easy but for now I'm unable to make it work. I'm a programmer and what I need to do is for example: if X = 2 and Y = 1 then Z = 1 if X = 3 and Y = 1 ...
0
votes
0answers
55 views

Computation doesn't Finish

I'm trying to solve some problem by the following code: ...