theorem Th81: :: JORDAN1A:81

for i, n being Nat
for C being connected compact non horizontal non vertical Subset of (TOP-REAL 2)
for p, x being Point of (TOP-REAL 2) st x in W-most C & p in west_halfline x & 1 <= i & i < len (Cage (C,n)) & p in LSeg ((Cage (C,n)),i) holds
LSeg ((Cage (C,n)),i) is vertical