theorem Th49:
for
P1,
P2 being
Subset of
(TOP-REAL 2) for
a,
b,
c,
d being
Real for
f1,
f2 being
FinSequence of
(TOP-REAL 2) for
p1,
p2 being
Point of
(TOP-REAL 2) st
a < b &
c < d &
p1 = |[a,c]| &
p2 = |[b,d]| &
f1 = <*|[a,c]|,|[a,d]|,|[b,d]|*> &
f2 = <*|[a,c]|,|[b,c]|,|[b,d]|*> &
P1 = L~ f1 &
P2 = L~ f2 holds
(
P1 is_an_arc_of p1,
p2 &
P2 is_an_arc_of p1,
p2 & not
P1 is
empty & not
P2 is
empty &
rectangle (
a,
b,
c,
d)
= P1 \/ P2 &
P1 /\ P2 = {p1,p2} )