Theorem: MyRing.two_mul (LeanInRome/S2_Basics/solutions/Solutions_S02_Proving_Identities_in_Algebraic_Structures.lean)

State before:
R : Type u_1
inst✝ : Ring R
a : R
⊢ 2 * a = a + a
Tactic:
rw [← one_add_one_eq_two, add_mul, one_mul]
State after:
no goals