for G being Group
for a being Element of G
for H1, H2 being Subgroup of G holds
( a in H1 "\/" H2 iff ex F being FinSequence of the carrier of G ex I being FinSequence of INT st
( len F = len I & rng F c= (carr H1) \/ (carr H2) & a = Product (F |^ I) ) ) by Th28;