Library
▹
Essentials
▹
Sets
Proposition 1.1.2.
Let
S
be a set. Then:
∅
⊆
S
Proof.
Let
x
∈
∅
.
⇒
def
↯
References.
http://metamath.tirix.org/0ss.html
https://leanprover-community.github.io/mathlib_docs/data/set/basic.html#set.empty_subset