import proveit
from proveit import A, B
from proveit import defaults
from proveit.logic.booleans.conjunction import false_and_true_negated
theory = proveit.Theory() # the theorem's theory
%proving nand_if_right_but_not_left
defaults.assumptions = nand_if_right_but_not_left.all_conditions()
AeqF = A.evaluation()
BeqT = B.evaluation()
FandB = BeqT.sub_left_side_into(false_and_true_negated, auto_simplify=False)
AeqF.sub_left_side_into(FandB, auto_simplify=False)
%qed