let p, q be QC-formula; :: thesis: still_not-bound_in (p => q) = (still_not-bound_in p) \/ (still_not-bound_in q)
( p => q is conditional & the_antecedent_of (p => q) = p & the_consequent_of (p => q) = q ) by QC_LANG2:46, QC_LANG2:def 11;
hence still_not-bound_in (p => q) = (still_not-bound_in p) \/ (still_not-bound_in q) by Th19; :: thesis: verum