theorem Th18: :: CALCUL_1:18

for Al being QC-alphabet
for f, g being FinSequence of CQC-WFF Al st len f > 1 & len g > 1 & Ant (Ant f) = Ant (Ant g) & 'not' (Suc (Ant f)) = Suc (Ant g) & Suc f = Suc g & Ant f |= Suc f & Ant g |= Suc g holds
Ant (Ant f) |= Suc f