jschulzb

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MaplePrimes Activity


These are questions asked by jschulzb

In Maple 2015, on windows 8.1 64-bit the command
series(2*x*(x-y)/y, y = 0, 3);
gives

which is incorrect. The answer is


You can notice the minus sign in front the the -2x is incorrectly typeset, which makes me wonder if it's a bug in the typsetting program and not series itself.

Please fix asap

Hi,

     I'm trying to numerically solve a PDE in Maple for different boundary conditions, however I'm having trouble even getting Maple to numerically solve it for simple boundary conditions.

I have cylindrical coordinates, r, z, theta, and I treat r = r(z, theta) for convenience to plot my solution surface. The initial coundary condition is that at z = epsilon (z = 0 is singular) , r = constant and of course r is periodic in theta. This is just a circle, and the analytical solution is know to be a half-sphere  r = sqrt(R^2 - z^2). I entered my initial boundary conditions into Maple, but it doesn't like the periodic one

IBC := { r(epsilon, theta) = R - epsilon__r,
              r(z, 0) = r(z, 2*Pi) };

pdsolve(
  PDE,
  IBC,
  numeric,
  indepvars = [z, theta],
  time = z,
  range = 0..2*Pi);
Error, (in pdsolve/numeric/par_hyp) Incorrect number of boundary conditions, expected 2, got 1

I'm not sure how to make this work, and then generalize it to more arbitrary intial slices r(epsilon, theta) = f(theta).

Here's the attached worksheet, ForMaplePrimesSUbmission.mw

Any help is appreciated,

Thanks

Hello, 

     I an trying to plot a function of a single variable, which is an implicit function of another variable, i.e. I want to plot F(x(t)), given that x and t are related through the implicit constraint equation f(x,t) = 0. Is there any plot stuctures in Maple that would easily let me do this? I tried implicit plot but this seems insufficient. 

     As an example, consider plotting F = x + x^2 subject to f = x + sin(x) + ln (t) = 0. I could also write this as  a function subject o a differential constraint, as is f = diff(x(t), t) + 1/t + (diff(x(t), t))*cos(x(t)) = 0 and try to use some sort of implicit DE plotting routine. 

     Any ideas?

Thanks!

Hi, 

     I have a question regarding pdsolve, or Solve from the PDEtools package. I have a set of equations relating partial derivatives, and I'd like to isolate certain terms without explicitly known the functions. I can do this for a single equation, but not multiple ones. I'm curious if Maple can currently handle a system of eqns like these easily, since I will be increasing the number of eqns in the future. Here's the code 

 

 

restart;

PDEtools:-declare(H=H(x,y,t)):

H(x, y, t)*`will now be displayed as`*H

(1)

eq1:= H[tt](x,y,t) = H[xx](x,y,t) + H[yy](x,y,t);

H[tt](x, y, t) = H[xx](x, y, t)+H[yy](x, y, t)

(2)

eq2 := diff(H[tt](x,y,t), t) = diff(H[tx](x,y,t), x) + diff(H[ty](x,y,t), y);

diff(H[tt](x, y, t), t) = diff(H[tx](x, y, t), x)+diff(H[ty](x, y, t), y)

(3)

eq3 := diff(H[tx](x,y,t), t) = diff(H[xx](x,y,t), x) + diff(H[xy](x,y,t), y);

diff(H[tx](x, y, t), t) = diff(H[xx](x, y, t), x)+diff(H[xy](x, y, t), y)

(4)

eq4 :=diff(H[ty](x,y,t), t) = diff(H[xy](x,y,t), x) + diff(H[yy](x,y,t), y);

diff(H[ty](x, y, t), t) = diff(H[xy](x, y, t), x)+diff(H[yy](x, y, t), y)

(5)

PDEtools:-Solve(eq3, H[xy]);

H[xy](x, y, t) = Int(diff(H[tx](x, y, t), t)-(diff(H[xx](x, y, t), x)), y)+_F1(x, t)

(6)

PDEtools:-Solve({eq1, eq2, eq3, eq4}, H[xy]);

Error, (in pdsolve/sys) the input system cannot contain equations in the arbitrary parameters alone; found equation depending only on {H[tt](x,y,t), H[xx](x,y,t), H[yy](x,y,t)}: H[tt](x,y,t)-H[xx](x,y,t)-H[yy](x,y,t)

 

 

 

 

Download PDESolveHelp.mw

Hi, 


     I've been playing around with the Physics package, and I'm confused on evaluaing derivatives of explicit funcitons of the coordinates. This code below doesnt behave as I would think. I'm trying to define z as a function of X[mu]*X[mu], and take diff(z, X[mu]). You can see that each method d_, diff,  disagree and none are satisfactory ansers. (Maple 2015, Windows 8.1 64-bit, Intel i5 Haswell) 

# Declare coordinates for 2 dimensions, flat space

restart:
with(Physics):
Setup(mathematicalnotation = true, dimension = 2):
Coordinates(X):

# Method 1: Using Define and various differential operators
Define(z):
z :=sqrt(R^2-X[mu]*X[mu]);
d_[mu](z(X));
d_[1](z(X));
diff(z, x1);  #This one is correct
diff(z, X[mu]); # off by 2

# Method #2: Using functions
# Off by a factor of 2
z2 := mu -> sqrt(R^2-X[mu]*X[mu]);
diff(z2(mu), X[mu]); # off by 2

 PhysicsDiffBug.mw

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