
theorem Th15:
  for P, Q being pcs-Str holds pcs-sum(P,Q) = pcs-Str (#
    (the carrier of P) \/ the carrier of Q,
    (the InternalRel of P) \/ the InternalRel of Q,
    (the ToleranceRel of P) \/ the ToleranceRel of Q #)
proof
  let P, Q be pcs-Str;
A1: the carrier of pcs-sum(P,Q) = (the carrier of P) \/ the carrier of Q by
Th14;
  the InternalRel of pcs-sum(P,Q) = (the InternalRel of P) \/ the
  InternalRel of Q by Th14;
  hence thesis by A1,Th14;
end;
