theorem :: MEASURE5:22 :: MEASURE5:36
  r <= p & r <= s implies not [.r,s.] c= ].p,q.[
proof
  assume that
A1: r <= p and
A2: r <= s;
  take r;
  thus r in [.r,s.] by A2,Th1;
  thus thesis by A1,Th4;
end;
