Consider the following premises. r_2 -> p_1. ~t_1. p_1 <-> t_1. r_2 or ~p_1. Can we infer r_2 from them? If possible, name the inference rules being used at each step.
 From p_1 <-> t_1, ~t_1 we can infer ~p_1 via biconditional elimination. From r_2 or ~p_1 we can infer p_1 -> r_2 via rewriting. From r_2 -> p_1, p_1 -> r_2 we can infer r_2 <-> p_1 via biconditional introduction. Finally, from r_2 <-> p_1, ~p_1 we can infer ~r_2 via biconditional elimination, which contradicts r_2. Therefore, the answer is no.