theorem Th49: :: QC_LANG3:49

for A being QC-alphabet
for p being Element of QC-WFF A
for V being non empty Subset of (QC-variables A) st p is biconditional holds
Vars (p,V) = (Vars ((the_left_side_of p),V)) \/ (Vars ((the_right_side_of p),V))