let A be QC-alphabet ; :: thesis: for F, H being Element of QC-WFF A st H is conjunctive holds
( F is_immediate_constituent_of H iff ( F = the_left_argument_of H or F = the_right_argument_of H ) )
let F, H be Element of QC-WFF A; :: 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 Th3;
hence ( F is_immediate_constituent_of H iff ( F = the_left_argument_of H or F = the_right_argument_of H ) ) by Th45; :: thesis: verum