{
  sorry
}
case inl
P : ℕ → Prop
n : ℕ
h : 8 ≤ n ∧ n ≤ 10
htri9 : n < 9
⊢ from_three_five n

case inr
P : ℕ → Prop
n : ℕ
h : 8 ≤ n ∧ n ≤ 10
htri9 : 9 ≤ n
⊢ from_three_five n
case inr
P : ℕ → Prop
n : ℕ
h : 8 ≤ n ∧ n ≤ 10
htri9 : 9 ≤ n
⊢ from_three_five n