## Contraction in Physics package...

So I have the following:

restart;
with(Physics):
Setup(mathematicalnotation=true,coordinatesystems=cartesian);
Define(A[mu](X));

First of all X ist defined in terms of (x,y,z,t). Is is also possible to define it in terms of (t,x,y,z) with t being mu=0.

When I do

alias(X=(t,x,y,z))

this applies only to this one vector and

d_[4] is still the time differentiation, right?

Then I wanted to construct the divergence

d_[~mu] A[mu](X);
TensorArray(%,performsumoverrepeatedindices=true);

This should give me sth like d1 A1 + ... + d4 A4, but it stays with d_mu A_mu ?!?

Why?

Is there also a "function" which does the contraction?

So if I have

f[mu,nu]=d_[mu] A[nu](X)

eval(f[mu,nu],nu=mu)

contract(%)

??

## How do i open this maple document?...

Hey MaplePrimes

I have a problem with opening some of my documents in maple. When i try to open them, a box pops up with the text "How do you want to open this file?" with the options "Maple Text, Plain Text, Maple Inputs". None of these options work (document is blank) and "Plain Text" and "Maple Inputs" causes maple to crash. Is it possible to recover the documents?

ps. when i try to upload one the documents this happens:

Maple Worksheet - Error
Failed to load the worksheet /maplenet/convert/Maple_docs_til_mat.mw .

## interface() problem...

I want to suppress  ~ when using assume()

I write:

restart;
interface(showassumed = 0);
assume(s>0);
s;

but s still appears with tilde?!?

## applyrule for different expressions...

restart;

eq1 := a[n+2]+4*a[n+1]+10*a[n]-5*n-1;

applyrule(a[n::anything] = n*p+q+b[n], eq1);

eq2 := a(n+2)+4*a(n+1)+10*a(n)-5*n-1;

applyrule(a(n::anything) = b(n)+n*p+q, eq2);

eq3 := a(n+2)+4*a(n+1)+10*a(n) = 5*n+1;

applyrule(a(n::anything) = b(n)+n*p+q, eq3)

So my question is: Why does the first one not work? the second one works as expected, but the third one again does not?!

## Trouble entering a partial differential equation i...

Good morning,

I've been having some trouble entering this expression in Maple 17.

My teacher suggested using this format, however, this format is from 2004 and certainly isn't recognized by the current version of Maple, as it keeps spitting back 0=0 no matter how many different ways I try to enter it.

Could anyone provide feedback on the correct syntax of how to enter this expression? Thank you very much for your time.

## ode bvp fluid problem...

how may i encounter this problem,

 >
 >
 >
 >
 (1)
 >
 (2)
 >
 >
 >
 >
 (3)
 >
 >
 >

h bcs

Is is possible to tell the latex output what to do if it finds a symbol?

Suppose I have the following expression:

O3^2 + k_O3NO

The normal latex output just takes it as it is and also translates k_O3NO to k_O3NO with the underscore.

I however want it to read (latex notation in math mode)

\left[ \text{O}_3 \right]^2 + k_{\text{O}_3\text{NO}}

So is that possible without changing everything manually?

edit: Just as a remark, the output at the moment for this expression reads

{{\it O3}}^{2}+{\it k\_O3NO}

and is kinda awful if compiled in latex...

Is it also possible for maple to latex realizing where a line-break is necessary?

## Plot of coupled functions and extraction of the da...

Hello.

I'd like to plot two coupled functions x=x(t) and y=y(t) given by expression R0 and R1 (see below) for the interval t=0.001..0.999 and then after that extract tha data from the graphs for functions x(t) and y(t).

How can I do that in easiest way?

I will appreciate you.

## Maple17 performance on a simple integral of ration...

Dear all,

I've just discover something quite surprising for me... It turns out like if Maple didn't take in account the linearity of the integral.

In the middle of a calculation, I need to compute the following integral

int(3628800 / (y * (1 / 2 + y)^11) - 3628800 / (y * (39 / 2 + y)^11), y = 39 / 2..infinity);

Maple 17 is not able to instantly answer me, and I'm not so patient... (I've waited more than 30s)

Nevertheless, if I ask Maple 17 to compute

3628800 * int(1 / (y * (1 / 2 + y)^11) - 1 / (y * (39 / 2 + y)^11), y = 39 / 2..infinity);

as well as

int(3628800/(y*(1/2+y)^11), y = 39/2..infinity)-int(3628800/(y*(39/2+y)^11), y = 39/2..infinity);

Maple 17 answer me instantly... which turn out to be quite surprising!

Is there someone, here, who has some ideas of what is happening in this calculation? Why Maple17 has this strange behaviour?

Tolliob

## Simplification of Expression...

Why does

5103*&Omega;*(5*sqrt(7)+16)/((1+2*sqrt(7))^(3/2)*(7+2*sqrt(7))*(-2+sqrt(7))*(14+sqrt(7))*(2*sqrt(7)-1)*(4+sqrt(7)))

not simplify to

sqrt(1+2*sqrt(7))*&Omega;

???

## The integration of Jacobi elliptic functions...

Hello everybody.

I'd like to share an observation about the integration of the Jacobi elliptic functions, in particularly the elliptic sine sn(x,k).

It's correct answer. But when I make the integration of the expression

according to the Handbook of Elliptic Integrals for Engineers and Scientists we have slightly another result

What is the difference?

## how to calculate potential energy in terms of gaus...

how to calculate potential energy in terms of gauss curvature?

## Error, number of indices exceeds rank...

Hello.

I have been trying to create a code to solve a structure by using FEM, but I keep getting an error that stops me from moving on.

Everytime I run my code, Maple gives me the error in the Title of my question:
"Error, number of indices exceeds rank"

Unfortunately I can't find any help in Maplesoft support for such error, and I need immediate help for that.

Can someone help me with that? Should I post my entire code?

Thanks!

## solve trigonometric system of equation with condit...

I want to solve this equation with assumptions!!!

restart;
assume(d::real, d>0):
assume(a::real, -0.01 < a, a < 0):
sys:={-800*Pi*a*cos(6.557377048*Pi*(3.470797713+d))/(a+1)^3 = -.9396060697, 800*Pi*a*sin(6.557377048*Pi*(3.470797713+d))/(a+1)^3 = -.3238482794};
solve(sys, {a,d},useassumptions=true, AllSolutions=true);

one of the solutions has true "a" but "d" is wrong, I want one true solution!

## Eigenvalues. Mechanical problem...

I solve a mechanical exercise but i had a problem.

I know M (mass) and K (stifness) matrices (4x4).

I want to solve the (λ2M+K)v=0  eigenvalue problem, where λ are the eigenvalues and v eigenvectors.

How can i solve this problem.  I tried with the Eigenvectors() command but it didn't give the right solution.

The Eigenvalues are okay, but the eigenvectors not

K := Matrix([[4*10^7,-1.50*10^7,2*10^7,0],[-1.50*10^7,1.50*10^7,0,1.50*10^7],[2*10^7,0,8*10^7,2*10^7],[0,1.50*10^7,2*10^7,4*10^7]]);

M:=Matrix([[121.90,99.048,-91.429,0],[99.048,594.29,0,-99.048],[-91.429,0,243.81,-91.429],[0,-99.048,-91.429,121.90]]);

w1,w2:=Eigenvectors(K,M);

Acoording with the book the right eigenvectors(shape mode) are:

[0.013 991,  0.034 233,  0.073 683,  0.090 573]
[0.035 637, 0, -0.032 213, 0]
[0 ,-0.034 233, 0, 0.090 573]
[-0.013 991, 0.034 233, -0.073 683, 0.090 573]

Thank you

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