let P be Subset of (TOP-REAL 2); ( P is being_special_polygon implies P is being_simple_closed_curve )
given p1, p2 being Point of (TOP-REAL 2), P1, P2 being Subset of (TOP-REAL 2) such that A1:
( p1 <> p2 & p1 in P & p2 in P )
and
A2:
( P1 is_S-P_arc_joining p1,p2 & P2 is_S-P_arc_joining p1,p2 )
and
A3:
P1 /\ P2 = {p1,p2}
and
A4:
P = P1 \/ P2
; TOPREAL4:def 2 P is being_simple_closed_curve
reconsider P1 = P1, P2 = P2 as non empty Subset of (TOP-REAL 2) by A3;
( P1 is_an_arc_of p1,p2 & P2 is_an_arc_of p1,p2 )
by A2, Th2;
hence
P is being_simple_closed_curve
by A1, A3, A4, TOPREAL2:6; verum