Theorem: LO.Modal.Standard.reducible_KT_S4 (Logic/Modal/Standard/Deduction.lean)

State before:
α : Type u_1
inst✝ : DecidableEq α
⊢ 𝐊𝐓 ≤ₛ 𝐒𝟒
Tactic:
apply normal_reducible_subset
State after:
case hSubset
α : Type u_1
inst✝ : DecidableEq α
⊢ Ax(𝐊𝐓) ⊆ Ax(𝐒𝟒)

State before:
case hSubset
α : Type u_1
inst✝ : DecidableEq α
⊢ Ax(𝐊𝐓) ⊆ Ax(𝐒𝟒)
Tactic:
simp only [Set.subset_union_left]
State after:
no goals