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Made by myself with Matlab

I, the copyright holder of this work, release this work into the public domain. This applies worldwide. In some countries this may not be legally possible; if so: I grant anyone the right to use this work for any purpose, without any conditions, unless such conditions are required by law.

function main ()

N=12; line_thickness=2.2; font_size=25; d=0.13; big_rad=10; ball_rad=0.5; ii=sqrt(-1);
red=[1, 0, 0]; green=[0, 1, 0]; blue=[0, 0, 1];
All=[red' green' blue'];

figure(1); clf; hold on; axis equal; axis off;

Theta=0:0.1:3*pi;
X=big_rad*cos(Theta);
Y=big_rad*sin(Theta);
plot(X, Y, 'linewidth', line_thickness, 'color', [0 0 0]);

for i=0:(N-1)
   z=big_rad*exp(i*ii*2*pi/N);
   place_text_smartly (z, font_size, i, d, sprintf('%d\\pi/%d', i, N/2), N);
   color_ball(real(z), imag(z), ball_rad, All(:, mod(i, 3)+1)');
end

scale=1.4;plot(scale*big_rad,  scale*big_rad)
scale=-1.4;plot(scale*big_rad,  scale*big_rad)

saveas(gcf, 'Normal_subgroup_illustration.eps', 'psc2')
saveas(gcf, 'Normal_subgroup_illustration.png')

function place_text_smartly (z, font_size, pos, d, tx, N)
 p=cos(2*pi/N)+sqrt(-1)*sin(2*pi/N);
 z = z + p^pos * d * font_size;
 shiftx=0.0003; shifty=0.03;
 x = real (z); y=imag(z);
 H=text(x+shiftx*font_size, y+shifty*font_size, tx);
 set(H, 'fontsize', font_size, 'HorizontalAlignment', 'c', 'VerticalAlignment', 'c')

 function color_ball(x, y, r, color)
    Theta=0:0.1:2*pi;
    X=r*cos(Theta)+x;
    Y=r*sin(Theta)+y;
    H=fill(X, Y, color);
    set(H, 'EdgeColor', 'none');

Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version.

Click on date to download the file or see the image uploaded on that date.

• (del) (cur) 13:18, 27 October 2005 . . en:User:Oleg_Alexandrov Oleg Alexandrov ( en:User_talk:Oleg_Alexandrov Talk) . . 648x623 (49214 bytes) (Made by myself with Matlab.)