The statement ~(p↔∼q) is
equivalent to (~p→q)
a tautology
a fallacy
equivalent to p↔q
~(p↔∼q)≡∼((p→∼q)∧(~q→p)≡∼((~p∨~q)∧(q∨p))
≡∼(~q∨~p)∨(~(q∨p))≡(~(q)∧~(~p))∨(~q∧~p)≡(q∧p)∨(~q∧~p)≡[(q∧p)∨(~q)]∧[(q∧p)∨(~p)]≡[(q∨(~q))∧(p∨(~q))]∧[(q∨(~p)) ∧(p∨(~p))]≡[t∧(~q∨p)]∧[((~p)∨q))∧t]≡(~q∨p)∧(~p∨q)≡(q→p)∧(p→q)≡p↔q
Alternative Solution. Use the following table.
From the last two colums, we get t~(p↔(~q))≡p↔q