exact if c:a ≤ b 
      then by
          unfold max
          unfold Nat.instMaxNat
          unfold maxOfLe
          simp [if_pos c]
          assumption
      else by
          unfold max
          unfold Nat.instMaxNat
          unfold maxOfLe
          simp [if_neg c]
R : Type ?u.124898
inst✝² : Ring R
inst✝¹ : DecidableEq R
X : Type ?u.124913
inst✝ : DecidableEq X
a b : ℕ
⊢ a ≤ max a b
no goals