reserve S for Subset of TOP-REAL 2,
  C,C1,C2 for non empty compact Subset of TOP-REAL 2,
  p,q for Point of TOP-REAL 2;
reserve i,j,k for Nat,
  t,r1,r2,s1,s2 for Real;
reserve D1 for non vertical non empty compact Subset of TOP-REAL 2,
  D2 for non horizontal non empty compact Subset of TOP-REAL 2,
  D for non vertical non horizontal non empty compact Subset of TOP-REAL 2;

theorem Th40:
  len SpStSeq S = 5
proof
  thus len SpStSeq S = len<*NW-corner S,NE-corner S,SE-corner S*> + len<*
  SW-corner S,NW-corner S*> by FINSEQ_1:22
    .= len<*SW-corner S,NW-corner S*> + 3 by FINSEQ_1:45
    .= 2 + 3 by FINSEQ_1:44
    .= 5;
end;
