prologues:=2 u=1.2cm; beginfig(1); path kruz; kruz:=fullcircle scaled 10u; z0= point 2 of kruz; z1= point 5.2 of kruz; z2= point 6.8 of kruz; z3= (subpath (4,6) of kruz) intersectionpoint (origin--2[origin,.5[z1,z2]]); z4= (subpath (6,0) of kruz) intersectionpoint (origin--10[origin,.5[z0,z2]]); z5= (subpath (2,6) of kruz) intersectionpoint (origin--10[origin,.5[z1,z0]]); z6= (z1--z0) intersectionpoint (z4--z5); z7= (z2--z0) intersectionpoint (z4--z5); z8= (z2--z0) intersectionpoint (z4--z3); z9= (z2--z1) intersectionpoint (z4--z3); z10= (z2--z1) intersectionpoint (z5--z3); z11= (z0--z1) intersectionpoint (z5--z3); draw kruz; draw z0--z1--z2--cycle; pickup pencircle scaled .2; draw z3--z4--z5--cycle; draw z1--z4; draw z2--z5; draw z0--z3; pickup defaultpen; draw z6--z9; draw z7--z10; draw z8--z11; label.llft(btex $M$ etex,z1); label.lrt(btex $K$ etex,z2); label.top(btex $S$ etex,z0); label.bot(btex $S'$ etex,z3); label.urt(btex $M'$ etex,z4); label.ulft(btex $K'$ etex,z5); label.rt(btex $O$ etex,(z7--z10) intersectionpoint (z6--z9)+(.5u,.3u)); label.ulft(btex $A$ etex,z6); label.urt(btex $B$ etex,z7); label.lrt(btex $C$ etex,z8+(.1u,.1u)); label.lrt(btex $D$ etex,z9); label.llft(btex $E$ etex,z10); label.llft(btex $F$ etex,z11); label.ulft(btex $K_1$ etex,.5[z11,z6]+(0,.2u)); label.urt(btex $M_1$ etex,.5[z7,z8]+(0,.2u)); label.ulft(btex $S_1$ etex,.5[z9,z10]+(.18u,0)); pickup pencircle scaled 2; drawdot(.5[z11,z6]); drawdot(.5[z7,z8]); drawdot(.5[z9,z10]); endfig; end;