let P be non empty compact Subset of (TOP-REAL 2); for q1, q2 being Point of (TOP-REAL 2) st P is being_simple_closed_curve & LE q1,q2,P holds
( q1 in Segment (q1,q2,P) & q2 in Segment (q1,q2,P) )
let q1, q2 be Point of (TOP-REAL 2); ( P is being_simple_closed_curve & LE q1,q2,P implies ( q1 in Segment (q1,q2,P) & q2 in Segment (q1,q2,P) ) )
assume that
A1:
P is being_simple_closed_curve
and
A2:
LE q1,q2,P
; ( q1 in Segment (q1,q2,P) & q2 in Segment (q1,q2,P) )
hereby q2 in Segment (q1,q2,P)
per cases
( q2 <> W-min P or q2 = W-min P )
;
suppose A3:
q2 <> W-min P
;
q1 in Segment (q1,q2,P)
q1 in P
by A1, A2, Th5;
then
LE q1,
q1,
P
by A1, JORDAN6:56;
then
q1 in { p where p is Point of (TOP-REAL 2) : ( LE q1,p,P & LE p,q2,P ) }
by A2;
hence
q1 in Segment (
q1,
q2,
P)
by A3, Def1;
verum end; suppose A4:
q2 = W-min P
;
q1 in Segment (q1,q2,P)
q1 in P
by A1, A2, Th5;
then
LE q1,
q1,
P
by A1, JORDAN6:56;
then
q1 in { p1 where p1 is Point of (TOP-REAL 2) : ( LE q1,p1,P or ( q1 in P & p1 = W-min P ) ) }
;
hence
q1 in Segment (
q1,
q2,
P)
by A4, Def1;
verum end; end;
end;
per cases
( q2 <> W-min P or q2 = W-min P )
;
suppose A5:
q2 <> W-min P
;
q2 in Segment (q1,q2,P)
q2 in P
by A1, A2, Th5;
then
LE q2,
q2,
P
by A1, JORDAN6:56;
then
q2 in { p where p is Point of (TOP-REAL 2) : ( LE q1,p,P & LE p,q2,P ) }
by A2;
hence
q2 in Segment (
q1,
q2,
P)
by A5, Def1;
verum end; end;