reserve P for Subset of TOP-REAL 2,
  f,f1,f2,g for FinSequence of TOP-REAL 2,
  p,p1,p2,q,q1,q2 for Point of TOP-REAL 2,
  r1,r2,r19,r29 for Real,
  i,j,k,n for Nat;

theorem
  P is_S-P_arc_joining p1,p2 implies P is_S-P_arc_joining p2,p1
proof
  given f such that
A1: f is being_S-Seq and
A2: P = L~f and
A3: p1=f/.1 and
A4: p2 = f/.len f;
  take g = Rev f;
  thus g is being_S-Seq & P = L~g by A1,A2,Th22;
  len g = len f by FINSEQ_5:def 3;
  hence thesis by A1,A3,A4,FINSEQ_5:65;
end;
