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

learn more… | top users | synonyms (4)

0
votes
1answer
23 views

Elements inside arrays seem to be strings rather than signed numbers

When I have code like b = Array[Subscript[be, #] &, {3, 1}] b = b /. {Subscript[be, k_] :> Subscript[-be, k] /; k > 1} I am noticing that Mathematica ...
0
votes
0answers
20 views

Solution of Laplace equation in Cylindrical Coordinates [on hold]

can anyone help me solving laplace eqn in cylindrical coordinates. I want the solution by Separation method resulting in Bessel function. 1/r d^2(u[x,theta,z,t])/dr^2 + d(u[x,theta,z,t])/dr + 1/r^2 ...
0
votes
2answers
53 views

Why does Solve give a wrong solution to an equation? [on hold]

I have got a following equation: -(c - x)/Sqrt[b^2 + (c - x)^2] + x/Sqrt[a^2 + x^2] == 0. Trying to solve it for x, so I evaluate ...
0
votes
0answers
33 views

Solve system of equations derived with the Lagrange approach

I am new here and hopefully you can answer my question. I have to pictures attached. The problem is as follows. I have 4 system equations, derived with the Lagrangian approach. Now I want to ...
3
votes
2answers
84 views

Finding solutions at non-differentiable points of a numerical function

Let's consider a 2D function we can evaluate numerically, but which is opaque to symbolic manipulation (this is just an example): ...
0
votes
0answers
40 views

Why does Mathematica not restrict the domains of Rational Expressions?

As taught in High School Mathematics: $$\begin{array}{ccl} \left\{ {(x-3)(x+3)\over 5(x+3)} : \ x\ne -3 \right\} & \ne & \left\{ {x-3\over 5} : \ x\in\mathbb{R} \right\} \\ \left\{ ...
0
votes
1answer
55 views

Problem in evaluation of a solution and plotting

I've written out a code which solves a equation and uses this solution to find "ph". ...
0
votes
0answers
18 views

handling the logistics function [on hold]

I have the problem, I have to handle the logistics function at two points. That is my initial and final cordenas cordenas. But do not know how to apply that formula. As would be the formula for this ...
1
vote
1answer
127 views

Singularity on a simple Plot

While solving quartic equation ...
-1
votes
0answers
23 views

Iterative Methods for Numerical Solution of Systems of Linear Algebraic Equations [closed]

i want to learn about Iterative Methods for Numerical Solution of Systems of Linear Algebraic Equations. Can you tell me what methods fall into this area? (Jacobiho, Gauss-Seidel, SOR etc........... ...
2
votes
1answer
96 views

Find tangency of InterpolatingFunction and circle

I am trying to use a system of equations to solve for the common tangent of a (polar) InterpolatingFunction and a circle. Unfortunately, both NSolve and FindRoot don't yield results, even when I ...
-1
votes
0answers
36 views

Numerical value of expression not solving function on Mathematica 10 [closed]

I'm trying to solve below calculation using Newton Raphson method: ...
0
votes
1answer
54 views

How to obtain a convergent solution iteratively for a linear system of equations

I am working on a problem that requires an iterative procedure to solve a linear system of equations, the system of equations in matrix form is: $$\underbrace{\begin{bmatrix} r_{11} & r_{12} ...
1
vote
2answers
59 views

Finding roots of a function with a varying parameter

So I'm brand new to Mathematica, and basically what I want to do is find the roots of a function at varying time intervals. The function I'm using is: ...
0
votes
1answer
58 views
-1
votes
1answer
46 views

How to assign variables to selected roots of a polynomial equation? [closed]

I have a polynomial equation like the below, and I want to assign variables to the roots that are not pure imaginary. How I can do this? ...
1
vote
1answer
48 views

How to change the expressions in terms of a specific variable?

I have a series of analytical equations: ...
0
votes
0answers
61 views

Regarding equation simplification

I have 2 variables, M and L. M == x y(z-k)^2 (2z+k)π / (3z^2) L == x y(z-k)(z+k)π / z^2 Is it possible to perform a simplication in Mathematica, such that I ...
0
votes
1answer
24 views

Is there a way to have FindInstance or Solve give only positive integer solutions?

I keep getting either negative or super long answers or super long negative answers in no particular order :\ ... Is there a way to only ask for positive solutions? (here we want 0 < x<(10^12+y) ...
0
votes
0answers
63 views

Implicit/Backward Euler method

I'm trying to solve (and plot) a differential equation using Explicit Euler method and Implicit Euler method. The Implicit method worked out jst fine but I have problems with Implicit one... I made ...
1
vote
0answers
57 views

How to find Pauli matrices

I wanted to find the Pauli matrices, so i wrote down this code: z = {{a, b}, {c, d}} i = {{1, 0}, {0, 1}} Solve[z.z == i, {a, b, c, d}] and mathematica gave me ...
0
votes
1answer
70 views

How to create a line due to requiriements?

Considering we have three lines, and know the intersection points (How to find intersection points of lines?) How can I draw a line that will cross the intersection point of the two lines and will be ...
1
vote
3answers
312 views

How to find intersection points of lines?

Considering I have three functions f1 = -x + 1; f2 = x - 1; f3 = x + 3; How can I find the intersection points of this functions? Thanks. This didn't work ...
0
votes
1answer
127 views

How to solve a large system of non-linear equations

I would like to solve Saha equations on Fe, which have 27 unknowns. Saha equations basically give you the ratios of the unknowns, but the unknowns are subject to constraints. What function shall I ...
1
vote
1answer
155 views

Solve a system of parametric equations

I have a system of parametric equations (with a total number of 8). I tried to solve this system by using Solve. I have not received an answer after about 4 hours! ...
0
votes
1answer
50 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 ...
0
votes
0answers
86 views

Solving Symbolically Equations with Vectors and Matrices

I want to solve equations with vector variables and vector/matrix parameters symbolically. As a basic example I would like to be able to solve something like $[I-aG]x=b$ where $a,b \in \mathbb{R}^l$ ...
0
votes
0answers
35 views

NSolve can not handle a PolyGamma equation

I would like to solve the following equations numerically: ...
1
vote
0answers
87 views

Mathematica reading my mind - Solve knows which variable to solve for

I was checking some of my algebra with the following code; ...
0
votes
1answer
94 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
1answer
33 views

WhenEvent for space variable

Can I use WhenEvent for space variable? For example ...
-1
votes
1answer
92 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
56 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 ...
0
votes
2answers
123 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. ...
10
votes
1answer
243 views

Does NRoots own an abstract counterpart? If not, can we write one?

We know when solving linear algebra equations, despite its abstract syntax, LinearSolve is much faster compared to Solve: ...
3
votes
3answers
150 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 ...
2
votes
2answers
73 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 ...
1
vote
1answer
176 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: ...
1
vote
1answer
67 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 ...
0
votes
1answer
64 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] $$ ...
0
votes
1answer
138 views

Plotting an extremly large output

I'm trying to plot the solutions of this determinant: ...
2
votes
3answers
84 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) ...
1
vote
1answer
72 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
1answer
38 views

NSolve & PrecisionGoal

I am using NSolve to find numerical solutions of a particular equation. I do not need the solutions to as high of a precision as the other numbers in my notebook. To improve run time (I am iterating ...
0
votes
1answer
80 views

NDSolve with initial condition: initial conditions did not evaluate to an array of numbers of depth 1(for 1D) or 2 (for 2D) on spatial grid

I have the following naive code to solve a PDE in two spatial dimensions (x,y) with periodic boundary conditions: ...
1
vote
2answers
56 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: ...
1
vote
0answers
41 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
0answers
71 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. ...
0
votes
1answer
56 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 ...