no goals
F : Type ?u.676324
α : Type u_1
β : Type ?u.676330
γ : Type ?u.676333
inst✝ : Group α
s t : Finset α
a b : α
⊢ preimage 1 ((fun x x_1 => x * x_1) a) (_ : Set.InjOn ((fun x x_1 => x * x_1) a) ((fun x x_1 => x * x_1) a ⁻¹' ↑1)) =
    {a⁻¹}
classical rw [← image_mul_left', image_one, mul_one]
no goals
F : Type ?u.676324
α : Type u_1
β : Type ?u.676330
γ : Type ?u.676333
inst✝ : Group α
s t : Finset α
a b : α
⊢ preimage 1 ((fun x x_1 => x * x_1) a) (_ : Set.InjOn ((fun x x_1 => x * x_1) a) ((fun x x_1 => x * x_1) a ⁻¹' ↑1)) =
    {a⁻¹}
rw [← image_mul_left', image_one, mul_one]