## how to use gamma in expression as symbol and not t...

I need to use gamma as a "free" symbol in pde that I pass to pdsolve, so that the latex comes out as \gamma OK in the solution.

in other words, the pde itself uses the symbol gamma (as it is written in the textbook and I want to keep it the same). This gamma is not the known constant gamma. Something similar to using alpha and beta or x and y.

But gamma in a known constant in Maple and I am worried this will affect some computation inside pdsolve if I use gamma  as known number in the PDE (even though I think it should not change the result of pdsolve as there are no other numbers in the PDE input, I just wanted to be safe).

I am not able to clear gamma

unassign(gamma)  gives error since it is protected.

Is  there a way around this? Should I use wrap the name with 'gamma'  or gamma for example?

Here is an example

pde := a*diff(w(x,y,z),x)+ b*diff(w(x,y,z),y)+c*diff(w(x,y,z),z)= alpha*x+beta*y+gamma*z+delta;

It is the gamma above I am worried about using in the input. What is the correct way to do this?

## what is the difference between D(y)(0)=C1 and eva...

I have thought that   D(y)(0)=C1  and  eval(diff(y(t),t),t=0)=C1  mean exactly the same thing which is derivative of y wr.t. "t" evaluated at specific point t=0 is C1.

If you agree they are exactly the same thing, then why dsolve works with both forms used for initial conditions if the option 'series' is not used.

When using the 'series' option, dsolve stops working when using  eval(diff(y(t),t),t=0) form? All else is the same.

ode:=diff(y(t),t$2)+3*diff(y(t),t)+2*y(t)=0; bc_form_1:=y(0)=C1,eval(diff(y(t),t),t=0)=C2; bc_form_2:=y(0)=C1,D(y)(0)=C2; sol1:=dsolve([ode,bc_form_1],y(t)); sol2:=dsolve([ode,bc_form_2],y(t))  Both the above work But now when I use the 'series' option, the first form stops working! ode:=diff(y(t),t$2)+3*diff(y(t),t)+2*y(t)=0;
bc_form_1:=y(0)=C1,eval(diff(y(t),t),t=0)=C2;
bc_form_2:=y(0)=C1,D(y)(0)=C2;
sol1:=dsolve([ode,bc_form_1],y(t),'series');
sol2:=dsolve([ode,bc_form_2],y(t),'series')


Is this a bug?

Just updated to Maple 2019.1  on windows 10.

## Why can not I create a plot in Maple 2019 correctl...

I have reinstalled Maple 2019 several times, including its latest update. But when trying to graph the following:

plot(sin(x), x = -2*Pi .. 2*Pi)

But I get this:

Error, (in plot) expected a range but received x = -2*Pi .. 2*Pi

And if I enter:

sin(x)

The result is:

2.73949338633639*10-116 + 2.73949338633639*10-116*I

When trying this:

plot3d(x*exp(-x^2 - y^2), x = -2 .. 2, y = -2 .. 2, color = x)

I get this:

And if I try it with Graph Theory:

with(GraphTheory);
G := Graph({{a, b}, {a, c}, {b, c}});
G := Graph 1: an undirected unweighted graph with 3 vertices and 3 edge(s)

DrawGraph(G)

Error, (in GraphTheory:-DrawGraph) invalid input: modp received I, which is not valid for its 2nd argument, m

I do not know what is the reason for this anomalous behavior of Maple 2019, it will be some software bug or it will be an error caused by my computer...
I would like to know if this problem happens to other people or just to me. Any help or guidance on this problem will be greatly appreciated.

Best regards

## no error message, but a wrong result...

In Maple 2019 it is not possible to change to "1-D Math Input".

But it is possible to convert (right mouse->convert to-> 1D Math Input)

In this mode I get the following results:

> 6/2*(1 + 2);
9
> 6/2(1 + 2);
3
I have the feeling the 2nd result is wrong.
If I change to "Maple input", I get the following result:
> 6/2(1 + 2);
9

In this editor, where I write this post, it is possible to insert Maple Math.
If I enter there "6/2(1 + 2)", in the preview is written "3".
and
If I enter there "6/2(1 + 2+9)", in the preview is written "3".

The parser gives no error message, but a wrong result.

If I enter nonsense, there is the following message "You have entered an invalid Maple expression".

Are you aware of this?

## What font does Tabluate() use?...

If I do:

df:=DataFrame(Matrix(3,4,[seq(1..12)]), rows=[a,b,c],columns=[A,B,C,D]);Tabulate(df, width=100)

The font that Maple uses for the Tablulate is much larger than the font used to display the Dataframe. How does one choose the font size that Tabluate() uses?

Peter

## solve with conditionals...

As always, thank you all in advanced.

I found this challenge by chance.

solve 615+x^2=2^y over integers.

I rushed to Maple and tried to solve it  with “solve” and "assuming" but I did not get results.

solve(615+x^2=2^y) assuming x::integer,y::integer   did not work.

How could this equation be suitably formulated for Maple to solve it?

## should pdsolve give this internal error?...

I was trying to see if Maple can solve this problem from my class textbook

When I tried boundary conditions all zero on the Laplace PDE in semicircular cylinder, pdsolve generates internal error.

The boundary conditions should not all be zero for nontrivial solution, but the question is why Maple generate this internal error? Is this a bug? Using Physics package 362, Maple 2019 on windows 10.

 > restart;
 > unassign('r,theta,z,f,H'); pde:=VectorCalculus:-Laplacian(u(r,theta,z),'cylindrical'[r,theta,z])=0; bc:=u(r,theta,0)=0, u(r,theta,H)= f(r,theta), u(r,0,z)=0, u(r,Pi,z)=0,u(a,theta,z)=0; sol:=pdsolve([pde,bc],u(r,theta,z)) assuming a>0,r0,theta>0,theta

 > unassign('r,theta,z,f,H'); pde:=VectorCalculus:-Laplacian(u(r,theta,z),'cylindrical'[r,theta,z])=0; bc:=u(r,theta,0)=0, u(r,theta,H)= 0, u(r,0,z)=0, u(r,Pi,z)=0,u(a,theta,z)=0; sol:=pdsolve([pde,bc],u(r,theta,z)) assuming a>0,r0,theta>0,theta

Error, (in assuming) when calling 'PDEAdvisor/2nd_order/Series/ThreeVariables'. Received: 'invalid input: rhs received _Z3, which is not valid for its 1st argument, expr'

 >

## Bug When Using IntegrationTools[Change] With Assum...

Good day,

I was recently using Maple 2019 for work on a project, and ran into an error. This error (which will be copied and pasted below for others to test) occurs when making assumptions across multiple lines (whether using the additionally function or not) while using IntegrationTools[Change]. It seems that, if during the process a variable that was within both the assumptions is subtracted from itself, the subtraction fails to happen and leaves what effectively equals 0 in the workings, making further workings impossible.

I'm wondering if anyone else is able to reproduce this error? I know the fix for it is to not disjoint the assumptions, but I am curious if others can easily reproduce it or if others have experiences with it!

As promised, below you will find my workings in order to reproduce this error!

Base Error:

restart;
assume(a>0,b>0,b>a,c>0,t>0);
interface(showassumed=0);
F := Int(sqrt(d-a*c^2*t),d=0...infinity);
assume(b>a);
IntegrationTools[Change](F,-a*t*c^2+d=-y,y)

Simple Fix:

restart;
assume(a>0,b>0,b>a,c>0,t>0);
interface(showassumed=0);
F := Int(sqrt(d-a*c^2*t),d=0...infinity);
IntegrationTools[Change](F,-a*t*c^2+d=-y,y)

Error Without Interface Change:

restart;
assume(a>0,b>a,c>0,t>0);
F := Int(sqrt(d-a*c^2*t),d=0...infinity);
assume(b>a);
IntegrationTools[Change](F,-a*t*c^2+d=-y,y)

restart;
assume(a>0,b>a,c>0,t>0);
interface(showassumed=0);
F := Int(sqrt(d-a*c^2*t),d=0...infinity);
IntegrationTools[Change](F,-a*t*c^2+d=-y,y)

## how to use Maple to prove an equation based on a k...

Dear Maple friends~

Recently I am thinking a question about how to use Maple to prove an equation based on a known partial differential equationand its boundary conditions.

Although I can Prove it with hand computation ,it still has some difficulty and it will be really hard if its partial differential equation become more complex(As a matter of fact, it will happen).So I think of Maple and want to take advantage of computer.However,I get few ideas how to realize it .The details are as follows：

alias(u=u(x,t)):
pde:=diff(u,t)-diff(u,x$2,t)+4*u^2*diff(u,x)=3*u*diff(u,x)*diff(u,x$2)+u^2*diff(u,x$3); N:=5;#actually N can be any positive integer! bcs:=eval(u,x=-infinity)=0,seq(eval(diff(u,x$ha),x=-infinity)=0,ha=1..N),eval(u,x=infinity)=0,seq(eval(diff(u,x\$ha),x=infinity)=0,ha=1..N);
E:=Int(u^4+2*u^2*diff(u,x)^2-diff(u,x)^4/3,x=-infinity..infinity);

#try to prove the following equation
diff(E,t)=0

The written proof is as follows:

Therfore,I submit such a problem and look forward your solutions and suggestions sincerely~

## Difficulties with function definition...

restart;
with(Physics);
with(LinearAlgebra);
N := 4;

Cf := Matrix(6, 6, (z, p) -> C[z, p, 1], shape = symmetric);
sigma[1] := Vector(6, [sigma[1, 1, 1], sigma[2, 2, 1], sigma[3, 3, 1], sigma[1, 2, 1], sigma[1, 3, 1], sigma[2, 3, 1]]);
varepsilon[1] := Vector(6, [varepsilon[1, 1, 1], varepsilon[2, 2, 1], varepsilon[3, 3, 1], gamma[1, 2, 1], gamma[1, 3, 1], gamma[2, 3, 1]]);
sigma[1] := Cf . (varepsilon[1]);

for i from 2 to N do
C[i] := Matrix(6, 6, (z, p) -> C[z, p, i], shape = symmetric);
sigma[i] := Vector(6, [sigma[1, 1, i], sigma[2, 2, i], sigma[3, 3, i], sigma[1, 2, i], sigma[1, 3, i], sigma[2, 3, i]]);
varepsilon[i] := Vector(6, [varepsilon[1, 1, i], varepsilon[2, 2, i], varepsilon[3, 3, i], gamma[1, 2, i], gamma[1, 3, i], gamma[2, 3, i]]);
sigma[i] := (C[i]) . (varepsilon[i]);
end do;

B[1] := 0;

for i to N do
Parameters(epsilon11c, C[1, 1, i], C[1, 2, i], C[2, 2, i], C[2, 3, i], R[i], A[i], B[i + 1], P);
end do;

g[1](r);
ux[1] := (x, r) -> epsilon[1][1]*x + g[1](r);
ur[1] := r -> A[1]*r + B[1]*1/r;
varepsilon[1][1] := epsilon11c;
varepsilon[1][2] := r -> (A[1]*r + B[1]*1/r)*1/r;
varepsilon[1][3] := r -> diff(ur[1](r), r);
varepsilon[1][3](R[2]);

for i from 2 to N - 1 do
g[i](r);
ux[i] := (x, r) -> epsilon[i][1]*x + g[i](r);
ur[i] := r -> A[i]*r + B[i]*1/r;
varepsilon[i][1] := epsilon11c;
varepsilon[i][2] := r -> (A[i]*r + B[i]*1/r)*1/r;
varepsilon[i][3] := r -> diff(ur[i](r), r);
varepsilon[i][2](r); i;
end do;
i;
varepsilon[2][2](r);

Hi everyone,

I am currently writing a code on maple and I am finding difficulties in this section.

When I define the functions this way, the result I get from the loop "for" for varepsilon[i][2](r) is the same and doesnt depend on i value. I also tried to define it another way that would give me different results but I would end up with being unable to replace the variable "r" with its values (I would get r(R2)).

I would be grateful if you could advice me with this matter.

## Maple 2019 Student license period...

Hi,

I want to figure out if the Student license offered by Maplesoft for Maple 2019 is perpetual or is just lasts for a year? If it lasts for just 12 months, is there another license I should get which isn't as expensive as the full license? I need it for my personal research.

## Is it possible to obtain a simpler solution to thi...

Maple is very good in solving PDE's. But this specific solution seems way too complicated when compared to Matematica solution, which I verified using Maple pdetest to be correct.

Is there a way to make Maple produce the simpler solution to this pde? simplify does nothing on the solution. May be by using a good HINT or such other option?

 > restart;
 > pde:=(a*y+b*x+c)*diff(w(x,y),x)-(b*y+k*x+s)*diff(w(x,y),y)=0;

 > sol:=pdsolve(pde,w(x,y))

 > mma_solution := w(x,y)= _F1( (2*s*x+k*x^2+2*c*y+2*b*x*y+a*y^2)/a );

 > pdetest(mma_solution,pde)

 >

Here is screen shot showing the other solution

## Factorizing simple expression...

How do I get Maple to factorize this simple expression without too much effort?

f:=3/2 + sqrt(8*k + 2) + 2*k

## possible bug in pdsolve. Too many levels of recurs...

Is the following a bug? I am using Maple 2019  64 bit with latest Physics package 357 on windows 10.

 > restart;
 > pde :=  diff(w(x,y,z),x)+(y^2- a*exp(alpha*x)*(x*y-1))*diff(w(x,y,z),y)+(c*exp(beta*x)*z^2+b*exp(-beta*x))*diff(w(x,y,z),z)= 0; sol:=pdsolve(pde,w(x,y,z));

Error, (in depends) too many levels of recursion

 > restart;
 > pde :=  diff(w(x,y,z),x)+ (b*exp(alpha*x)*y^2 + a*exp(beta*x)*(beta- a*b*exp((alpha+beta)*x)))*diff(w(x,y,z),y)+(c*z^2*exp(gamma*x)+ d*z + k*exp(-gamma*x))*diff(w(x,y,z),z)= 0; sol:=pdsolve(pde,w(x,y,z));

Error, (in depends) too many levels of recursion

 > restart;
 > pde :=  x*diff(w(x,y,z),x)+ ( a1*exp(alpha*x)*y^2 + beta*y+ a1*b2^2*x^(2*beta)*exp(alpha*x))*diff(w(x,y,z),y)+(a2*x^(2*n)*z^2*exp(lamba*x)+(b2*x^n*exp(lambda*x) - n)*z + c*exp(lambda*x))*diff(w(x,y,z),z)= 0; sol:=pdsolve(pde,w(x,y,z));

Error, (in depends) too many levels of recursion

 >