Consider the following premises. forall x: U(x) <-> W_2(x). ~W_2(a). U(a) or t_2. Can we infer u or t_2 from them?
 From forall x: U(x) <-> W_2(x) we can infer U(a) <-> W_2(a). From U(a) <-> W_2(a), ~W_2(a) we can infer ~U(a). From ~U(a) we can infer ~U(a) or u. Finally, from ~U(a) or u, U(a) or t_2 we can infer u or t_2. Therefore, the answer is yes.