{
  sorry
}
case inr.inl
P : ℕ → Prop
n : ℕ
h : 8 ≤ n ∧ n ≤ 10
htri9 : 9 ≤ n
htri10 : n < 10
⊢ from_three_five n

case inr.inr
P : ℕ → Prop
n : ℕ
h : 8 ≤ n ∧ n ≤ 10
htri9 : 9 ≤ n
htri10 : 10 ≤ n
⊢ from_three_five n
case inr.inr
P : ℕ → Prop
n : ℕ
h : 8 ≤ n ∧ n ≤ 10
htri9 : 9 ≤ n
htri10 : 10 ≤ n
⊢ from_three_five n