theorem Th12: :: VALUAT_1:12

for Al being QC-alphabet
for A being non empty set
for v being Element of Valuations_in (Al,A)
for p, q being Element of CQC-WFF Al
for J being interpretation of Al,A holds (Valid ((p '&' q),J)) . v = ((Valid (p,J)) . v) '&' ((Valid (q,J)) . v)