theorem
  modRel(5) = {[0,1], [1,2], [2,3], [3,4], [4,0]}
proof
  thus modRel(5) = succRel(5) \/ {[5-1,0]} by Th41
    .= {[0,1], [1,2], [2,3], [3,4], [4,0]} by Th9, ENUMSET1:10;
end;
