Theorem: Tutorial.mul_one (Solution/Advanced/Algebra/Lecture1.lean)

State before:
A : Type ?u.7038
G : Type
inst✝¹ : Ring A
inst✝ : Group G
a : G
⊢ a * 1 = a
Tactic:
apply mul_left_cancel (a := a⁻¹)
State after:
A : Type ?u.7038
G : Type
inst✝¹ : Ring A
inst✝ : Group G
a : G
⊢ a⁻¹ * (a * 1) = a⁻¹ * a

State before:
A : Type ?u.7038
G : Type
inst✝¹ : Ring A
inst✝ : Group G
a : G
⊢ a⁻¹ * (a * 1) = a⁻¹ * a
Tactic:
simp
State after:
no goals