Unanswered Questions

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restart;
with(PDETools);
diff(r(t), t)-(diff(a[3](t), t))*r(t)/a[3](t)+a[1](t)*p[3](t)-3*r(t)*r(t) = 0;
                                        
dsolve(diff(r(t), t)-(diff(a[3](t), t))*r(t)/a[3](t)+a[1](t)*p[3](t)-3*r(t)^2 = 0, r(t));

 it does not give any solution ,please help.

how to solve optimal system of vector   fields in lie theory in maple?

What is a suitable replacement for eliminate?

Here is my code:

 

A := {x[5] = x[2]/x[1], x[6] = x[3]/x[2], x[7] = x[1]/x[4], x[8] = (2*x[2]+x[4])/(2*x[1]+x[3]+x[4])};
B := {x[1], x[2], x[3], x[4], x[8]};

([eliminate])(A, B);
([eliminate])(A, B minus {x[1]});
([solve])(A, B);


In the older versions of Maple the first example of eliminate would return same result as the solve example, but with current version I need to resort to the second example.

Hi, I need to calculate some discrete variational problems, but it's a hard work just by hand.

Is there any toolboxes about the discrete variational computation? Or how to design a program to do that?

In particular, I need to realize the functions:

1. the linearized operator and the adjoint operator of some expressions.

       For example:

       the linearized operator of u(n,m+1)u(n+1,m) is u(n+1,m)Tm+u(n,m+1)Tn

       the adjoint operator is u(n+1,m-1)T^(-1)m+u(n-1,m+1)T^(-1)n,

       (The latter is just the discrete Euler operator.)

      Tm, Tn is the shift operator, T^(-1) is the inverse operator of T.

2. discrete Euler-Lagrange equation.

I am not familar with the maple, please help!

Thanks.

How do I introduce the first derivative of M when i<> k and aij when i <> j and aii in Maple?

 

 

Am trying to teach myself "circle inversion" to solve circle geometry problems.  Towards this end I wrote a Maple 7 program to draw a Pappus chain of circles.  Pappus lived around 200AD, and I read that he considered this problem ancient!  

   The output diagram may not come out on this forum, but it comes out as a collection of tangential circles, and I have no problems with that.  In drawing the circles I was thinking of using the infinity symbol.  The following line uses the infinity, but with a minus sign.  Maple is "happy" with this and outputs square braces, suggesting an empty list?  I changed the program by omitting the -ve sign - and Maple came up with an error message.  I would have expected the output to include the value zero  ie [0]  I think it is just that the infinity symbol is not allowed in the seq command. 

[seq( i, i=0..-infinity )];  #???  why the -?,

 

In the next part I define X, Y and rad as the coordinates and radii of a sequence of circles: subscript i, ranging from start to nterm, (for the number of terms).  These are set at 1 and 286.   The program works OK with these values, but if the variable start is changed to zero, 0, it doesn't work.  I thought I might have a division by zero, but can't find one.  I also drew a circle with a radius of zero - no problem!  (...except it's difficult to see:-))   

   My main puzzle is why does it come up with the error message "invalid subscript selector" when the variable start is set to 0?

With i=start=0 I am asking it to draw a circle of radius zero at some specified coords - but it doesn't like it!  

  Any comments would be appreciated.  Merry Christmas.

David

 

 

restart:

# # # # # # # # # # # # # # # # # # # # # # # # # # # #

# Pappus Chain of circles

# # # # # # # # # # # # # # # # # # # # # # # # # # # #

with(plots):

with(plottools):

#Maple 7

#r is ratio of AC/AB = diam of large circle, to a smaller internally tangential one

r:=1.35:

#Why will start=0 not work?

start:=1:

#nterm=286 is smallest value where axes have "true" origin of (0.0)

#nterm<= 285 puts "x-axis" below y=-0.6

nterm:=286:

X := [seq( 0.5*r*(1+r)/(((i*(1-r))^2)+r), i=start..nterm )]:

 

Y := [seq( i*r*(1-r)/(((i*(1-r))^2)+r), i=start..nterm )]:

rad:=[seq(0.5*r*(1-r)/((i*(1-r))^2+r), i=start..nterm)]:

[seq( i, i=0..-infinity )];  #???  why the -?

#Gives [] output with -ve sign:  empty list?  Why is 0 not included?

# Not allowed to use with seq

#ccc:=[seq(circle([X[i],Y[i]],rad[i]), i=1..5)]:  #nops(X))]:

ccc:=[seq(circle([X[i],Y[i]],rad[i]), i=start..nterm)]:

#c := circle([1,1], 0, color=red):

#plots[display](c, scaling=constrained);

plots[display](ccc, scaling=constrained);

 

OUTPUT

 

Hello

Long time asker of minimization problems here.

Following on from my question on 2D packing.

I found this "solved" problem for packing 3D items efficiently. See Illustration 6.13

https://www.researchgate.net/file.PostFileLoader.html?id=59938b635b49527571134c33&assetKey=AS%3A527790252490752%401502846410852

Some discrepancies with constraint set-up (first one), number of variables and the optimized solution.

3DbinPack2.mw

 

Hello

When I export a worksheet table as HTML,MATH EXPRESSIONS: GIF the resulting .html file is 100% readable.

screenshot:

But when i send the html file to myself over email, I get gibberish

The (acer) code for the top is... .....Equation(Standings[id]:-mu &+- Standings[id]:-sigma....

and below opponents rating: ....Cell(Equation(thetable[id][':-losses'][r][1] &+- thetable[id][':-losses'][r][2],......

Anyone shed?

Does any body have example of maple code for solving optimal control problem in deterministic model using Pontryagin's maximum (or minimum) principle?

While using a version of Maple on the inverse symbolic calculator I first described my idea for a new constant in 1999 and other people named it after me, calling it the MRB constant. While looking for an applied math purpose for the MRB constant =sum((-1)^k (k^(1/k)-1),k=1..infinity), I noticed that the absolute value of its summand is the interest rate to multiply an investment k times in k years=k^(1/k)-1. Any ideas on how this might be related to other subjects?

Say I want to use multiples commands on an expression

simplify(expand(eval(expr,x=y+1)))

 

Now similar I could use

(simplify@expand)(expr)

but how do I do it with sth like eval which needs extra arguments

(simplify@expand@eval(x->y, x=y+1))(f)

??

t := 5;
                               5
u := exp((1/2)*x-2*t*(1/3));
                            /1     10\
                         exp|- x - --|
                            \2     3 /
plot(u(x), x = -4 .. 4);


this is the exact solution graph

while below is the approximate solution graph

h := -1;
                               -1
t := 5;
                               5
u := exp((1/2)*x)*(1+t*(27*h^4+108*h^3+240*h^2+256*h)/2^7+t^2*(27*h^4+24*h^3+168*h^2)/2^7+(1/3)*t^3*(9*h^4+16*h^3)/2^6+(1/4)*t^4*h^4/2^4);
                         6877    /1  \
                         ---- exp|- x|
                         192     \2  /
plot(u(x), x = -4 .. 4);

 

Please help me

I'm getting the message

Secure Connection Failed

when trying to get into this forum using the latest version of Firefox.
For writing this I used Internet Explorer.

The message continues with:

An error occurred during a connection to mapleprimes.com. You have received an invalid certificate. Please contact the server administrator or email correspondent and give them the following information: Your certificate contains the same serial number as another certificate issued by the certificate authority. Please get a new certificate containing a unique serial number. Error code: SEC_ERROR_REUSED_ISSUER_AND_SERIAL
    The page you are trying to view cannot be shown because the authenticity of the received data could not be verified.
    Please contact the website owners to inform them of this problem
.

 

Has anybody else experienced the same?
What to do? 

Please, anyone with usefull informations to hint me. Looking forward to your favorable response. 

Thanking you in advance

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