have := h (r 1) (sr 0)
case mk
n : ℕ
hn : 3 ≤ n
h : ∀ (a b : DihedralGroup n), a * b = b * a
⊢ False
case mk
n : ℕ
hn : 3 ≤ n
h : ∀ (a b : DihedralGroup n), a * b = b * a
this : r 1 * sr 0 = sr 0 * r 1
⊢ False