When typing 

z:=exp(I*2*Pi/3);
convert(z,'sincos')

Maple evaluates the intermediate result which is cos(2*Pi/3)+I*sin(2*Pi/3) and  gives

Is there a way to tell it not to do this? I'd like to see the result as when typing

'cos(2*Pi/3)+I*sin(2*Pi/3)'

Is there an option or method to tell Maple not to immediate evaluation in the above? it can do evaluate next time the expression is used.

Should Maple handle this error internally and may be give no solution if it can't solve it instead of this  error?

When setting boundary condition to zero, maple gives error below. Heat PDE in a sphere. No angle dependency. Only the radial part.

unassign('r,u,t');
pde:=diff(u(r,t),t)= 1/r*diff(r*u(r,t),r$2); #Laplacian in spherical
ic:=u(r,0)=1;
bc := u(1,t) =0;
pdsolve([pde,ic,bc],u(r,t),HINT =boundedseries(r=0)) assuming t>0

Error, (in assuming) when calling 'ln'. Received: 'when calling 'ln'. Received: 'numeric exception: division by zero''

Adding assumptions such as 0<r,r<1 did not help.

Physics version 348. Maple 2019 on windows 10. Is there something I am doing wrong? 

Why does Maple display eval(diff(f(r),r),r=C)=0;  differently when C is a number?

unassign('f,C,r');
eval(diff(f(r),r),r=C)=0;
eval(diff(f(r),r),r=5)=0;

I wanted the first one to display the same as the second one. First one looks confusing. it looks like taking derivative w.r.t to C. Is there a way to make the first one look like:

I am learning how to use dchange in Maple. I can do  something as dchange(x=t^2) OK, but I need to do dchange(x=t^n) where "n" is meant to be a parameter that I can later use subs on to set it to any number I want.  But I do not know how to tell Maple that "t" is the new variable and that "n" is meant to be used as constant or parameter.

As an example, this works

n:=2;
ode:=x^2*diff(z(x),x)=0;
PDEtools:-dchange({x=t^n},ode,{t})

But this does not work

n:='n';
ode:=x^2*diff(z(x),x)=0;
PDEtools:-dchange({x=t^n},ode,{t});
subs(n=2,%)

It used "n" above as new variable. So the dependent variable which was z(x) became z(t,n). 

So I need to tell Maple that "t" is the new variable only and not "n" as well. 

Is it possible to do this in Maple?

Maple 2019 on windows.

Is this an expected behaviour for simplify/size? 

I was simplifying a result from pdsolve, but did not check that the solution was null or () before calling simplify.

It turns out that  simplify((),size)  returns size for this. I find this is very strange.

I would have expected it to return ().

I can fix this by checking that sol is not null before calling simplify ofcourse. But the question is, why does simplify((),size) return size? What is the logic for this? From help:

The simplify(expr, size) calling sequence is used to attempt simplifying the expression size, performing only collections and simple decomposition of fractional powers in the coefficients - sometimes taking advantage of linear factors when they exist. No other mathematical simplifications of the expression or its subexpressions is performed. These operations, while simple and with low computational cost, may remarkably structure the expression and reduce its size.
 

is it possible what happens is this: becuase "sol" was null, the call simplify(sol,size) has actually become simplify(size) and the result is size.  So because the first slot in the call was (), it was ignored during the call and the first parameter became size insteal of sol?

Maple 2019 on windows 10.