What Is The Difference Between ∈ And ⊆?
The symbol /∈ is used to denote that an element is not in a set. For example, π /∈ Z, √ 2 /∈ Q (the second one might take some thought to prove). ⊆ The symbol ⊆ is used to denote containment of sets. For example, Z ⊆ Z ⊆ […]