Theorem: Section5sheet2Solutions.WeakGroup.mul_one (FormalisingMathematics2024/Solutions/Section05groups/Sheet2.lean)

State before:
G : Type
inst✝ : WeakGroup G
a✝ b c a : G
⊢ a * 1 = a
Tactic:
apply mul_eq_of_eq_inv_mul
State after:
case h
G : Type
inst✝ : WeakGroup G
a✝ b c a : G
⊢ 1 = a⁻¹ * a

State before:
case h
G : Type
inst✝ : WeakGroup G
a✝ b c a : G
⊢ 1 = a⁻¹ * a
Tactic:
rw [inv_mul_self]
State after:
no goals