I did not think I was using "Plain Text".

Please tell me how to include 1D Maple code in a posting so that it looks (to some approximation) like 1D Maple code.  I've done that in a number of postings, such as www.mapleprimes.com/forum/howdoyousolvelargesystemequationsapplyingrules#comment-13264

 but other times it comes out with tags, and I really am confused, because I don't know what I'm doing differently when it works and when it doesn't.

I did not think I was using "Plain Text".

Please tell me how to include 1D Maple code in a posting so that it looks (to some approximation) like 1D Maple code.  I've done that in a number of postings, such as www.mapleprimes.com/forum/howdoyousolvelargesystemequationsapplyingrules#comment-13264

 but other times it comes out with tags, and I really am confused, because I don't know what I'm doing differently when it works and when it doesn't.

Instead of evaluating at t=0, you could take the limit as t -> 0. 

plots:-arrow([0,0,0], map(limit, convert( nhat, list), t = 0), shape = cylindrical_arrow,    color=black);

Instead of evaluating at t=0, you could take the limit as t -> 0. 

plots:-arrow([0,0,0], map(limit, convert( nhat, list), t = 0), shape = cylindrical_arrow,    color=black);

For me, the main problem with the editor is that it's much more difficult than it should be to switch between "Normal" format and "Formatted" (which I want to use for entering 1D Maple code) and back again.  For example, suppose I start in Normal, then want to switch to Formatted for one paragraph.

It sometimes works, but I have to be careful that I'm really 
in a new paragraph, otherwise everything from the start of 
the previous paragraph will be Formatted.  Now I want to switch
back.

 

But it seems I didn't really get a new paragraph, because it switches the Formatted stuff back to Normal.  I had to highlight the last paragraph and make it Formatted.

And then sometimes I get postings such as www.mapleprimes.com/forum/areabetweencurves#comment-13204

that come out in source format.  I don't know why that happened, or how to correct it.

Here's a more elementary approach for the 257-gon, obtaining 24 pairs of equations of the form { x + y = a, x y = b}, solving these and at the end obtaining a (horrendously complicated) expression for 2 cos(2 Pi/257) in terms of nested square roots.   Presumably, considerable simplification is possible...

View 4541_257gon.mw on MapleNet or Download 4541_257gon.mw
View file details

So, will this crack the 257-gon? 

> bounds:= proc(t,s)
uses Typesetting;
    mrow(Typeset(-t), mo("≤"), Typeset(s), mo("≤"), 
      Typeset(t))
    end proc;

> bounds(2,x);

(well, MaplePrimes can't show it properly I think, but the 
output looks OK)

> bounds:= proc(t,s)
uses Typesetting;
    mrow(Typeset(-t), mo("≤"), Typeset(s), mo("≤"), 
      Typeset(t))
    end proc;

> bounds(2,x);

(well, MaplePrimes can't show it properly I think, but the 
output looks OK)

I guess it's limited by the capabilities of "solve".

The help page for ?convert,radical says

If the argument of a trigonometric function is of the form n/120*Pi where n is an integer, then Maple converts the function to radical form.
 

Maple can convert cos(2*Pi/17) to a RootOf:

> convert(2*Pi/17, RootOf);

RootOf(1-8*_Z-40*_Z^2+80*_Z^3+240*_Z^4-192*_Z^5-448*_Z^6+128*_Z^7+256*_Z^8, .9324722294)

But it won't solve this in terms of radicals.

> convert(%,radical);

RootOf(1-8*_Z-40*_Z^2+80*_Z^3+240*_Z^4-192*_Z^5-448*_Z^6+128*_Z^7+256*_Z^8, index = 4)

Let P be the polynomial in this RootOf.

> P := op(1,%);

P doesn't factor over the rationals, but it does factor if you adjoin sqrt(17).

> factor(P, sqrt(17));

-(16*_Z^4+4*_Z^3+4*_Z^3*sqrt(17)-6*_Z^2+2*_Z^2*sqrt(17)+4*_Z-2*_Z*sqrt(17)-1)*(-16*_Z^4-4*_Z^3+4*_Z^3*sqrt(17)+6*_Z^2+2*_Z^2*sqrt(17)-4*_Z-2*_Z*sqrt(17)+1)

With _EnvExplicit set to true, solve will handle quartics.

> _EnvExplicit:= true:

   S := solve(%%);

The solution cos(2*Pi/17) turned out to be the fifth of these.

> S5:= S[5];

S5 := -1/16+(1/16)*sqrt(17)+(1/16)*sqrt(34-2*sqrt(17))+(1/8)*sqrt((17*sqrt(34-2*sqrt(17))+3*sqrt(17)*sqrt(34-2*sqrt(17))-14*sqrt(17)-34)/sqrt(34-2*sqrt(17)))

Maple can do a bit of simplification on this.

> simplify(radnormal(S5), size);

-1/16+(1/16)*sqrt(17)+(1/16)*sqrt(34-2*sqrt(17))+(1/8)*sqrt((1/2*(-3-sqrt(17)))*sqrt(34-2*sqrt(17))+3*sqrt(17)+17)

Actually, there are several technical meanings of "elementary" in mathematics (see e.g. eom.springer.de/E/default.htm), and that is not one of them.  The closest is in number theory, where methods that don't involve complex analysis are called "elementary".

It's not so much the evaluation rules for seq, as the evaluation rules for a procedure definition: variables in a procedure definition are never evaluated when the procedure is defined.  So

> i := 3;

  x -> i * x;

produces x -> i*x, not x -> 3*x. 

The standard way to produce a function from an expression, where the variables are evaluated, is to use unapply.  So I'm surprised that this hasn't been suggested:

> L := [seq](unapply(i*x, x), i = 1 .. 3);

I found the old "My recent posts" quite useful.  This change is definitely not an improvement from my point of view.

Where on the site do I find "Who's online"?  I don't see it anywhere.