let n be Nat; :: thesis: for P being Subset of
for p1, p2, q1 being Point of st P is_an_arc_of p1,p2 & P /\ (LSeg p2,q1) = {p2} holds
P \/ (LSeg p2,q1) is_an_arc_of p1,q1
let P be Subset of ; :: thesis: for p1, p2, q1 being Point of st P is_an_arc_of p1,p2 & P /\ (LSeg p2,q1) = {p2} holds
P \/ (LSeg p2,q1) is_an_arc_of p1,q1
let p1, p2, q1 be Point of ; :: thesis: ( P is_an_arc_of p1,p2 & P /\ (LSeg p2,q1) = {p2} implies P \/ (LSeg p2,q1) is_an_arc_of p1,q1 )
assume that
A1: P is_an_arc_of p1,p2 and
A2: P /\ (LSeg p2,q1) = {p2} ; :: thesis: P \/ (LSeg p2,q1) is_an_arc_of p1,q1

per cases ( p2 <> q1 or p2 = q1 ) ;

suppose p2 <> q1 ; :: thesis: P \/ (LSeg p2,q1) is_an_arc_of p1,q1

then LSeg p2,q1 is_an_arc_of p2,q1 by Th15;
hence P \/ (LSeg p2,q1) is_an_arc_of p1,q1 by A1, A2, Th5; :: thesis: verum

end;

suppose A3: p2 = q1 ; :: thesis: P \/ (LSeg p2,q1) is_an_arc_of p1,q1

then A4: LSeg p2,q1 = {q1} by RLTOPSP1:71;
q1 in P by A1, A3, Th4;
hence P \/ (LSeg p2,q1) is_an_arc_of p1,q1 by A1, A3, A4, ZFMISC_1:46; :: thesis: verum

end;

end;