Metamath Proof Explorer


Theorem 0ss

Description: The null set is a subset of any class. Part of Exercise 1 of TakeutiZaring p. 22. (Contributed by NM, 21-Jun-1993)

Ref Expression
Assertion 0ss ∅ ⊆ 𝐴

Proof

Step Hyp Ref Expression
1 noel ¬ 𝑥 ∈ ∅
2 1 pm2.21i ( 𝑥 ∈ ∅ → 𝑥𝐴 )
3 2 ssriv ∅ ⊆ 𝐴