let H, F be Element of QC-WFF ; :: thesis: ( H is conjunctive implies ( F is_immediate_constituent_of H iff ( F = the_left_argument_of H or F = the_right_argument_of H ) ) )
assume H is conjunctive ; :: thesis: ( F is_immediate_constituent_of H iff ( F = the_left_argument_of H or F = the_right_argument_of H ) )
then H = (the_left_argument_of H) '&' (the_right_argument_of H) by Th4;
hence ( F is_immediate_constituent_of H iff ( F = the_left_argument_of H or F = the_right_argument_of H ) ) by Th62; :: thesis: verum