input geometriesyr12;
beginfig(1);
  pair A,B,C,D,I,J,K,L;
  A=u*(1,1);
  B=u*(5,1.5);
  C=A rotatedabout(B,-90);
  D=B rotatedabout(A,90);
  draw A--B--C--D--cycle;
  path astro;
  I=1/2[A,B];
  J=1/2[B,C];
  K=1/2[C,D];
  L=1/2[D,A];
  astro=J--arccercle(J,I,B)--arccercle(I,L,A)--arccercle(L,K,D)--arccercle(K,J,C)--cycle;
  draw hachurage(astro,60,0.25,1);
  draw astro;
  trace cotation(A,B,-4mm,-2mm,btex $2c$ etex);
  draw codesegments(A,I,I,B,2);
  draw codesegments(B,J,J,C,2);
  draw codesegments(C,K,K,D,2);
  draw codesegments(D,L,L,A,2);
  draw codeperp(A,B,C,5);
  draw codeperp(B,C,D,5);
  draw codeperp(C,D,A,5);
endfig;
end