exact le_trans (two_mul_le_sq (one_lt_iff_two_le.mp lt)) (by simp)
case inr.inr
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 i : M
pos : 0 < i
lt : 1 < i
⊢ 2 * i ≤ i ^ 2 + 1
no goals