Hallo everybody,

I just started to use maple and I think I need some help from more experienced users.
I would like to transform the stationary Navier Stokes equations to toroidal coordinates.

The definition of my coordinate system is as follows:
x = -r * cos(sigma)
y = cos(Theta) * ( R + r * sin(sigma) )
z = sin(Theta) * ( R + r * sin(sigma) )

I tried to define the coordinate system and transform each term of the equation:

div( rho * CC) = -grad(p) + div(Tau)

I can transform the pressure gradient. However, I get an error for the divergence of the tensors.
Could someone please give me a hint on how to get the divergences?

Thanks!
Uwe

My code is printed below:

restart: with(plots): with(LinearAlgebra): with(VectorCalculus): with(linalg):

#torus defintion
x := -r*cos(sigma);
y := cos(Theta)*(R+r*sin(sigma));
z := sin(Theta)*(R+r*sin(sigma));
R := .35;
AddCoordinates(torus1[r, sigma, Theta], [cos(Theta)*(R+r*sin(sigma)), sin(Theta)*(R+r*sin(sigma)), -r*cos(sigma)]);
SetCoordinates(torus1[r, sigma, Theta]);

#pressure gradient
PressureGradient := Gradient(p(r, sigma, Theta, t));

#left hand side
c := vector(3, ([Cr, Ctheta, Cx])(r, sigma, Theta, t));
rhoCC := rho*multiply(c, transpose(c));
LHS := Divergence(rhoCC)

 of solution to plot a function?

with(DEtools):

sys := {diff(x(t), t) = y(t), diff(y(t), t) = -(1+(1/100)*t)^2*x(t), x(0) = -1, y(0) = 2};

sys := {diff(x(t), t) = y(t), diff(y(t), t) = -(1+(1/100)*t)^2*x(t), x(0) = -1, y(0) = 2}

dsn := dsolve(sys, numeric);

dsn:=proc(x_rkf45) ... end proc

My question is how to use dsn to plot functions E(t) and I(t) with respect to t in a given interval [t1,t2].

E(t)=0.5*(diff(x(t),t)^2+w^2*x(t)^2), w=1+t/100.  I(t)=E(t)/w.

Many thanks to everyone helping me : )

Hi to all

I had solve a set of ODEs using rkf45 method and I had plot it's Diagram now I need to have area under my diagram.what should I do? what is code?

hi all

i have a set of complex numerics, so:

1- i want the numeric with least valence(potency) in imagin particle,

2- i want print the real particle of this numeric.

for example:

A:= .5464691235-.4473247264*I, -.4563184747+1.*10^(-14)*I, .5464691235+.4473247264*I

i want print: -.4563184747

plz help

hi.please see attached file below and help me

Error, (in solve) cannot solve expressions with diff(diff(diff(f4(x), x), x), x) for diff(diff(f4(x), x), x)

thanks..error.mw

Hello please,

Can some one help me find inverse of this fucntion 

f(x) = binomial(x+r-1, x)*((d*x+1)/(1+d*x+(1/2)*b))^x*((1/2)*b/(1+d*x+(1/2)*b))^r/(d*x+1)

Thanks.

Question regarding solving the equation systems. 

See maple file for equations. 

Equation_questions_.mw

I'm doing some easy calculations in Maple 2015, but Maples units are acting weird:

I would say that h and h/1 should be the same, but 1/h should give me 1/400 m^2*K*W^-1

If I try to input 1/U__0 it gives me 1/400 m^2*K*W^-1, just like expected

Am I doing anything wrong? Can it be because of my settings?

I'm running Maple 2015 on a Macbook pro running OSX 10.11

I want to plot E with respect to t.

I typed the sys of this equation and try to plot it with DEplot but failed.

This is the code

DEplot([sys], [x(t), y(t), E(t)], t = -25 .. 25, [[x(0) = -.3, y(0) = .2]], scene = [E(t), t], stepsize = 0.5e-1, linecolor = red, arrows = none);

The error is Error, (in DEtools/DEplot/CheckDE) derivatives must be given explicitly.

Eager to know the answer, please help me . Thanks very much.

I am puzzled at the lack of output in using the solve command.  Bellow is some sample code; the main part being the for k loop with values 1 to 5.  k=1 gives complex solutiions, and k=2 to 5 gives real values.  If the for loop is restricted to from 2 to 5 and the printf statement uncommented, everthing works fine.

I have tried other methods like sols:=fsolve(a*x^2+k*x+c, x, complex);  to little avail. I realize the equation is an easy quadratic & is easy to solve by the usual formula, but I'm interested in how the solve command works.  It seems to perform caculations, without any error messages - which I find frustrating!

The code after the for k from... ...do loop just illustrates examples where solve works - some with complex coefficients - which to my mind makes my problem more enigmatic!  I'm using Maple 7 and am just wondering if the solve command has been made easier to use?

   Any help or comments would be most appreciated.

Kind regards,

  David

#Program to investigate the solve function.  Putting k=1 gives complex solutions which halts the program.
> restart:
> interface(imaginaryunit, errorbreak=0, errorcursor=true, labelling=false):
> with(SolveTools):
> a:=1:c:=1:
>

################################
> for k from 1 to 5 do
>   sols:=solve(a*x^2+k*x+c, x):  # assuming x::complex;
>   #printf("k=%d  sols[1]=%5.2f  sols[2]=%5.2f\n", k,eval(sols[1]), eval(sols[2]));
> end do:  #for k

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

> printf("End of for loop\n\n");
> sols2:=solve(x^2+I);
> sols2[1];
> sols2[2];
> #sols3:=solve(a*x^3+x^2-I+2);
> solve(z^(I+1)+I,z);
> evalc(op(1,%));  #c=Cartesian
> k:=1:
> sols4:=solve(a*x^2+k*x+c, x):
> #evalc(op(1,%));  #c=Cartesian
> print("Evaluating sols4");
> eval(sols4);
> sols4[1];
> sols4[2];

So I am using the with(Student[MultivariateCalculus]); package to find the maximum and minimum of the fumction xyz to the given constraint: LagrangeMultipliers(x*y*z, [x^2+4*y^2+4*z^2-4], [x, y, z]) and I got 14 points. But to find the global maximum/minimum I need to evaluate all these points in the main function xyz. I tried converting it to a list and doing something and checked out this thread but it's only for single variable stuff so I am not sure how to extrappolate it to my case.

http://www.mapleprimes.com/questions/202529-Evaluating-A-Function-At-More-Than-One-Point#

These were my points by the way, Yeah lots.

[0, 0, 1], [0, 0, -1], [0, 1, 0], [0, -1, 0], [2, 0, 0], [-2, 0, 0], [(2/3)*sqrt(3), (1/3)*sqrt(3), (1/3)*sqrt(3)], [-(2/3)*sqrt(3), -(1/3)*sqrt(3), -(1/3)*sqrt(3)], [(2/3)*sqrt(3), (1/3)*sqrt(3), -(1/3)*sqrt(3)], [-(2/3)*sqrt(3), -(1/3)*sqrt(3), (1/3)*sqrt(3)], [(2/3)*sqrt(3), -(1/3)*sqrt(3), (1/3)*sqrt(3)], [-(2/3)*sqrt(3), (1/3)*sqrt(3), -(1/3)*sqrt(3)], [(2/3)*sqrt(3), -(1/3)*sqrt(3), -(1/3)*sqrt(3)], [-(2/3)*sqrt(3), (1/3)*sqrt(3), (1/3)*sqrt(3)]

Hi everyone,

I wanted to know if it was possible to store symbolic variables in a vector because I have a function of 10 variables which I want to write with Σ, Π and A(l), A being my vector of symbolic variables...

Thank you for your time


Benjamin

Hi. I have this strange error.

Whenever I type D(f)(x) into the maple prompt, the program adds a whitespace between D(f) and (x), so I get the wrong output. I have to go back and delete the space manually. Here is a picture. http://prntscr.com/8vji4k

I type 'D(f)(x)'  and the software displays 'D(f) (x) ' in the prompt, with the extra space.

I am using maple 2015 if that helps, but I think I had the same error with Maple 18

I did not add a space. I literally just entered f:=x->x^2 -3*x + 2; D(f)(x)

but the computer adds a space as I type D(f)(x).

Also I'm not sure why the space ruins the expression

What i am supposed to get is  ' 2x - 3 '

I used to convert the expression to latex code and copy the code to MathType, the insert the expression.

Is there any easier way?

I want the expression I inserted is modifiable, so copy from Maple and paste to Word is not what I want.

Are there any examples of network solutions such as mine systems in Maple.
I wrote in the Maple system of partial differential equations describing the process of filtration combustion.
I'm a novice. I do not quite understand how to solve it.
Online a lot of "simple" examples. I need something very similar to my case.

Model03.mw