u:=0.7cm;
t:=1.5pt;
r:=2pt;

beginfig(1);
z0=(0,0);
z1=z0+3.5cm*dir15;
z2=z0+3cm*dir55;
draw z0--z1--z2--cycle;
label.lrt(btex$a$etex, 0.5[z0,z1]);
label(btex$A$etex, z2+0.3cm*dir-90);
label.ulft(btex$b$etex, 0.5[z0,z2]);
label(btex$B$etex, z1-0.45cm*dir(0.5[angle(z2-z1),angle(z0-z1)]));
label.urt(btex$c$etex, 0.5[z1,z2]);
label(btex$C$etex, z0+0.6cm*dir(0.5[angle(z1),angle(z2)]));
endfig;

beginfig(2);
u:=2.5cm;
draw  for i=0 step 10 until 350:  u*dir i..  endfor  cycle;
pickup pencircle scaled t;
draw  for i=0 upto 13:  u*dir(360*i/14+90)--  endfor  cycle;
pickup pencircle scaled 0.5;
draw (0,0)--u*dir90;
label.rt(btex$30\,\rm cm$etex, 0.5u*dir90);
endfig;

beginfig(3);
u:=2.5cm;
draw  for i=0 step 10 until 350:  u*dir i..  endfor  cycle;
pickup pencircle scaled t;
draw  for i=0 upto 8:  u*dir(360*i/9+90)--  endfor  cycle;
pickup pencircle scaled 0.5;
draw (0,0)--u*dir90;
label.rt(btex$50\,\rm cm$etex, 0.5u*dir90);
endfig;

bye