let P be pcs-Str ; for a being set holds
( the carrier of P c= the carrier of (pcs-extension P,a) & the InternalRel of P c= the InternalRel of (pcs-extension P,a) & the ToleranceRel of P c= the ToleranceRel of (pcs-extension P,a) )
let a be set ; ( the carrier of P c= the carrier of (pcs-extension P,a) & the InternalRel of P c= the InternalRel of (pcs-extension P,a) & the ToleranceRel of P c= the ToleranceRel of (pcs-extension P,a) )
set R = pcs-extension P,a;
A1:
the carrier of (pcs-extension P,a) = {a} \/ the carrier of P
by Def39;
A2:
the InternalRel of (pcs-extension P,a) = [:{a},the carrier of (pcs-extension P,a):] \/ the InternalRel of P
by Def39;
the ToleranceRel of (pcs-extension P,a) = ([:{a},the carrier of (pcs-extension P,a):] \/ [:the carrier of (pcs-extension P,a),{a}:]) \/ the ToleranceRel of P
by Def39;
hence
( the carrier of P c= the carrier of (pcs-extension P,a) & the InternalRel of P c= the InternalRel of (pcs-extension P,a) & the ToleranceRel of P c= the ToleranceRel of (pcs-extension P,a) )
by A1, A2, XBOOLE_1:7; verum