yes i'm still here figthing against math: now I have a trigonometric question to ask.

In a Tk canvas I drow a circle, then I want to place a variable number of dots in the circumference, equally spaced in radiants (well.. I lost 3 hours before looking at sin to discover it accepts in radiants and not in degrees..).

In the below example I work with a canvas 610x610 and I create a circle with radius 300 to have same space around it.

Then I create some fat_dot aka little circles but I must have some offset misplaced and after some radiants my fat_dots are a bit outside of the circumference.

Where I'm failing?

Is my radiants computation right?

Notice that I need to store coordinates of all fat_dot and their ids to achieve other operations later on.

Where I need your precious advice is in the draw subroutine.

use warnings;
use strict;
use Tk;

my $top = new MainWindow;
my $canv;
# offset use to decide the square around a given point
my $offset = 4;
my $num_of_points = 4;
my @points;     # ([x1,y1],[x2,y2]...)
my @tk_points;     # (tk-canvas,..)

$top->Label(-text => "How many points?")->pack(-side => 'left');
$top->Entry(-width => 3,-borderwidth => 4, -textvariable => \$num_of_p
+oints)->pack(-side => 'left'); 
$top->Button(    -padx=> 5,
                -text => "draw",
                -borderwidth => 4, 
                -command => sub{&draw($num_of_points)})->pack(-side =>
+ 'left');

$top->Button(    -padx=> 5,
                -text => "clear",
                -borderwidth => 4,
                -command => sub{@points = ();
                        map{ $canv->delete($_) }@tk_points;
                        })->pack(-side => 'left');


# new toplevel for the circle
$canv=$top->Toplevel(-title=>'Points in a cirlce')->Canvas(-background
+=>'gray',
    -width => 610, 
    -height => 610)->pack;

# the big cirlce
my $circle = $canv->createOval(10,10,600,600,
               -fill => 'red', 
        -outline => 'yellow',
        -width => 5,
               -tags =>['circle'],
               -stipple => 'gray12',
          );

# draw the center at 305 305
fat_dot(305,305);

MainLoop;

sub fat_dot {
    # center of the new fat dot
    my ($x,$y) = @_;
    # canvas and top left and bottom right coords of the 
    # rectangle where the cirlce will be draw
    my ($x1,$y1,$x2,$y2) = ($x-$offset,$y-$offset,$x+$offset,$y+$offse
+t);
    my $dot = $canv->createOval($x1,$y1,$x2,$y2,-fill => 'black');
    return $dot;
}

sub draw{
    my $num = shift;
    print "received $num as num of points\n";
    # sin and cos they think in rad not in degrees!!
    my $ang = 3.141592653589793238462643383279 * 2 / $num;
    print "angle: $ang radiants\n";
    my $cur = 0;
    for (1..$num){
        my $x = 305 + int(300*sin($cur));
        my $y =  10 + 300 - int (300*cos($cur));
        print "at $cur radiants point at: $x $y\n";
        my $dot = fat_dot($x,$y);
        $cur+=$ang;
        push @points,[$x,$y];
        push @tk_points,$dot;
    }    
}
[download]

Thanks in advance for looking.

L*