beginfig(1); numeric u v w; u=1cm; path a, b,c ,d ; z1=(0,0); z2=(12u,0); z3=(4u,7u); z4=0.5[z1,z2]; z5=0.5[z2,z3]; z6=0.5[z3,z1]; z7=z4+(z2-z1) rotated 90; z8=z5+(z3-z2) rotated 90; z9= whatever[z4,z7]= whatever[z5,z8]; v=sqrt((z9-z1) dotprod (z9-z1)); w=v*0.5; a = fullcircle scaled 2v ; b= a shifted z9; draw z1--z2--z3--cycle; draw b; draw z9; draw z1--z5 dashed evenly; draw z2--z6 dashed evenly; draw z3--z4 dashed evenly; z10=whatever[z1,z5]=wathever[z2,z6]; draw z10; z11=whatever[z1,z2]=whatever[z3,z3+(z9-z4)]; z12=whatever[z2,z3]=whatever[z1,z1+(z9-z5)]; z13=whatever[z3,z1]=whatever[z2,z2+(z9-z6)]; draw z3--z11 dashed withdots; draw z1--z12 dashed withdots; draw z2--z13 dashed withdots; z14=whatever[z3,z11]=whatever[z1,z12]; z15=whatever[z1,z5]=whatever[z2,z6]; z16=0.5[z14,z9]; draw z14--z9; z17=0.5[z1,z14];z18=0.5[z2,z14];z19=0.5[z3,z14]; c= fullcircle scaled v; d=c shifted z16; draw d; pickup pencircle scaled 2pt; draw z9; draw z14; draw z15; draw z16; draw z4; draw z5; draw z6;draw z17; draw z18; draw z19; label.ulft(btex $B$ etex,z1); label.urt(btex $C$ etex,z2); label.top(btex $A$ etex,z3); label.bot(btex $A'$ etex,z4); label.urt(btex $B'$ etex,z5); label.ulft(btex $C'$ etex,z6); label.bot(btex $A_1$ etex,z11); label.urt(btex $B_1$ etex,z12); label.ulft(btex $C_1$ etex,z13); label.bot(btex $O$ etex,z9); label.urt(btex $G$ etex,z15); label.ulft(btex $H$ etex,z14); label.lft(btex $\Omega$ etex,z16); label.ulft(btex $A_2$ etex,z19); label.rt(btex $B_2$ etex,z17); label.rt(btex $C_2$ etex,z18); endfig; end