Earlier today (30/12/2018), I answered a fairly routine question  relating to solving the PDE for a vibrating string problem where the initial string profile was given by a piecewise function. No big deal - a fairly simple answer. Only thing that struck me at the time as odd/unusual, was that 2-3 days ago there was a very (very!) similar problem which I had also answered.

These two problems were posted from different usernames, but I did reference the earlier problem in my solution to the later one, just because they were so similar.

Both of these questions (and obviously my answers) have now "disappeared" -how/why?

1. I can (just about?) understand that an OP might be allowed to delete his/her question, but I am surprised that (s)he can delete a complete thread - ie after response(s) have been provided
2. I suspect that both questions came from the same individual employing different user names (why?). I guess this is pretty much impossible for MapleSoft to verify, particularly if the OP has multiple email addresses??
3. Would I be correct in assuming that this is a method for students to get their homework" done whilst leaving little/no trace for their academic supervisors to find?
4. Since all trace of both questions have disappeared and I can't actually remember the usernames (or emails with which they are associated), presumably the OP could repeat this behaviour indefinitely?

Hi every body:

I have six ODEs in two case with their initial conditions: 

case 1:

eqs1:= diff(r[1](t), t, t)+.68041478*(diff(r[1](t), t))+732.61274*r[1](t)-0.11751824e-2*V(t) = -0.52084940e-2*q(t), 2.03*10^(-8)*(diff(V(t), t))+4.0650406*10^(-7)*V(t)+0.11751824e-2*(diff(r[1](t), t)) = 0, diff(q(t), t, t)+(9.5199780*(q(t)^2-1))*(diff(q(t), t))+1006.9998*q(t) = -2192.5091*(diff(r[1](t), t, t));
ics1 := V(0) = 0, q(0) = 0.1e-2, (D(q))(0) = 0, r[1](0) = 0, (D(r[1]))(0) = 0;

case 2:

eqs2:= diff(r[2](t), t, t)+3.3737665*(diff(r[2](t), t))+52672.540*r[2](t)-0.93177795e-2*V(t) = 0.18358493e-2*q(t), 2.03*10^(-8)*(diff(V(t), t))+4.0650406*10^(-7)*V(t)+0.11751824e-2*(diff(r[1](t), t))+0.93177795e-2*(diff(r[2](t), t)) = 0, diff(q(t), t, t)+(9.5199780*(q(t)^2-1))*(diff(q(t), t))+1006.9998*q(t) = -2192.5091*(diff(r[1](t), t, t))+772.79848*(diff(r[2](t), t, t));

ics2 := V(0) = 0, q(0) = 0.1e-2, (D(q))(0) = 0, r[2](0) = 0, (D(r[2]))(0) = 0;

How can i solve numeric stiff the ODEs and plot V(t) in case 2 for t=0..2?

tnx...

Hey there,

I've been struggling for a few days to integrate a function using rkf45.

For some context, I wish to numerically intergrate a function K * s_R (K,a,w) dK using runge kutta over a 2D grid of (a,w) values. Essentialy, performing the same sort of K-integral many different times for slightly different combinations of a and w. For one such (a,w) combination, the function looks something like this:

and rkf45 works just fine, and returns a numeric result. On the other hand, for a different combination of (a,w), the function looks like this:

and an attempt to perform rkf45 returns the following error: "cannot evaluate the solution past the initial point, problem may be complex, initially singular or improperly set up."

Here is a simplified version of my maple document for reference MaplePrimePleaseHelp.mw.

I'm happy to clarify anything that may be confusing and any thoughts or suggestions would be greatly appreciated.

Thank you!

please guide me how to write a simple code for Newton method to solve the following system of nonlinear equations
D= diagonal of A
L= lower triangular
U= upper Triangular
 

Download NM.mw
 

Download NM.mw

1) I want to visualize the probabilities of normal law. I used a technique ( a little heavy) ( see appendix) and I wonder if there is a way to do better ?

2 ) How do I calculate the probabilities of p( a<X<b) and p( X>c / X<d ) ?

3) How do I calculate the inverse probability in Maple. I only find the inverf(p) command under Maple TA?

NormaleVisualizationCourbe.mw

partial differential equation question??

u_tt = 9u_xx

_{boundary conditions : u (0,t) = (2,t) = 0}

_{initial conditions : u (x,0) = f(x) = { x(2-x)   ,0<x<1     ,      x   ,1<x<2  = 0 , t>0 ,}

                         u_t (x,0) = 0 , 0<x<2

I have a physics question I need to program it by Maple , Can you help me to solve ? Its Problem 9.34 from Griffiths

Hi,

I'm a beginner in programing with Maple.

Maple has an algorithm "LinearSolve". 

I'm trying - just for fun - to generate an algorithm to solve a linear system of equations according to the Gauss-Jordan-method.

The linear System is given by:

M1*x=b

(in the worksheet: M1 is a matrix, point (1)

b is a vector, point (2) and x is a vector too and is the solution of system, point (3)).

Point (3) is to check - after the generated algorithm points out the solution - if the algorthm is working fine.

The augmented matrix M2 is given by <M1|b>, point (4).

First, I want to generate zeros under the main diagonal of matrix M1 in the augmented matrix M2.

In the worksheet there is my idea to do this, but I get a (perhaps simple) error message ("Error, Invalid if statement termination"). But I don't know what I'm doing wrong...

Perhaps someone can have a look on my idea (link to the file) and give me a hint?

Thanks a lot for your help!!

LGS_Gauss-Jordan.mw

I am working on an Isoperimetric problem.

I have two différential dL and dA. And I am seeking the function y for wich the two différentials are collinear.

So I want "dL/dA=constant"

I tried many expression, but I don't know how to express the "= constant"
I tried also (dL/dA)'=0 but no workable answer...

Thank's for your help !

Hi!

I have the following problem

> restart:with(plots): Digits := 60:
> A:=42403:
> B:=269.95:
> C:=269.95:
> J1:=0.55:
> J2:=1.02:
> a:=196200:
> b:=14342220:
> c:=1589220:
> k:=157.08/0.0875:
> sys := {A-B*diff(x(t),t)=J1*diff(x(t),t,t)+C*(x(t)-y(t)),k*(J2*diff(y(t),t,t)-C*(x(t)-y(t)))=-(a+b*(diff(y(t),t)^2)/k^2+c*diff(y(t),t,t)),  D(x)(0) = 157.08, D(y)(0)=0, D(y)(10)=157.08,  D(x)(10) = 154.98}:
> dsn1 := dsolve(sys,numeric):
Error, (in dsolve/numeric/BVPSolve) matrix is singular

I would like to extract the unique values of a few sets in a list (L1) and insert them in another list (L2) without the sets.

L1:=[{3,5},{5,4}]:

L2:=[3,5,4]:

Could anyone help me with a bit of code so this works for all values in sets in a list?

I use the command 'labels = [x, Im(f)]'

to change the labels of my plots, but this time I need to put some "different" characters. i. e., \^{c} (in LaTeX notation).

How can I do this on Maple?

I need a help from someone who knows the GRTensor commands.

How do I write the last two terms of this equation of motion?How do I define Lagrangian matter, too?

My master said that I will do these calculations in the classic worksheet  maple18.

K² G_mn= (1/2) T_mn + (C₀/2) R_abgl T^ag T^bl g_mn+ 3 C₀ R_brs(mT_n)^b T^sr – C₀ L_m R_ab T^ab g_mn + C₀ R_ab T^ab T_mn+ 2 C₀  L_m R_mrns T^rs + C₀ ∇_a∇_r(T_(m^r T_n)^s)- C₀ ∇_s∇_r(T^sr T_mn)

Lm =-(1/4) F_mn F^mn 

Hi,

I can’t export a csv file.
The 'export' command returns a numeric value ?QuestionDataExport2.mw