Consider the following premises. T(c) or ~R_1(c). forall y: R_1(y) <-> T(y). Can we infer R_1(c) <-> T(c) from them?
 From forall y: R_1(y) <-> T(y) we can infer forall y: T(y) -> R_1(y). From forall y: T(y) -> R_1(y) we can infer T(c) -> R_1(c). From T(c) or ~R_1(c) we can infer R_1(c) -> T(c). Finally, from R_1(c) -> T(c), T(c) -> R_1(c) we can infer R_1(c) <-> T(c). Therefore, the answer is yes.