theorem Th21: :: JORDAN3:21

for f being FinSequence of (TOP-REAL 2)
for p being Point of (TOP-REAL 2) st f is unfolded & f is s.n.c. & p in L~ f & p <> f . ((Index (p,f)) + 1) holds
(Index (p,(Rev f))) + (Index (p,f)) = len f