theorem Th10: :: MSUALG_8:10

for x, y, Y being set
for X being Subset of (EqRelLatt Y) st x in Y & y in Y holds
( [x,y] in "\/" X iff ex f being FinSequence st
( 1 <= len f & x = f . 1 & y = f . (len f) & ( for i being Nat st 1 <= i & i < len f holds
[(f . i),(f . (i + 1))] in union X ) ) )