Theorem: LO.FirstOrder.Arith.Model.two_mul_two_eq_four (Arithmetization/Vorspiel/Lemmata.lean)

State before:
M : Type u_1
inst✝⁵ : Zero M
inst✝⁴ : One M
inst✝³ : Add M
inst✝² : Mul M
inst✝¹ : LT M
inst✝ : M ⊧ₘ* 𝐏𝐀⁻
a b c : M
⊢ 2 * 2 = 4
Tactic:
rw [←one_add_one_eq_two, mul_add, add_mul, mul_one, ←add_assoc,
  one_add_one_eq_two, two_add_one_eq_three, three_add_one_eq_four]
State after:
no goals