Consider the following premises. p <-> t_1. p <-> t_1. Can we infer t_1 <-> p from them?
 From p <-> t_1 we can infer p -> t_1. From p <-> t_1 we can infer t_1 -> p. Finally, from t_1 -> p, p -> t_1 we can infer t_1 <-> p. Therefore, the answer is yes.