apply deMorganSmall₂
l : List Prop
h₁ h₂ : Prop
t : List Prop
h : h₁ ∧ andN (h₂ :: t)
⊢ ¬(¬h₁ ∨ orN ((¬h₂) :: map Not t))
case a
l : List Prop
h₁ h₂ : Prop
t : List Prop
h : h₁ ∧ andN (h₂ :: t)
⊢ ¬¬h₁ ∧ ¬orN ((¬h₂) :: map Not t)