| a ∈ st1 ⊦ st0[a, st1[a]] ∪ (st1 -- a) = st0 ∪ st1, a ∈ st0 |
⊦ st1 = st2 ↔ (∀ a. (a ∈ st1 ↔ a ∈ st2) ∧ st1[a] = st2[a])
a ∈ st1 ⊦ a ∈ st0, ∀ a0. (a0 ∈ st0[a, st1[a]] ∪ (st1 -- a) ↔ a0 ∈ st0 ∪ st1) ∧ (st0[a, st1[a]] ∪ (st1 -- a))[a0] = (st0 ∪ st1)[a0]
Used terms: st0 ∪ st1, st0[a, st1[a]] ∪ (st1 -- a)