Subset

• Subset #Card
  • A subset $A \subset X$ is defined by: $$A \subset X \iff (x \in A \implies x \in X)$$

Back

A subset $A \subset X$ is defined by: $$A \subset X \iff (x \in A \implies x \in X)$$

Lean

Set.Subset (s ⊆ t) / ∀ x, x ∈ s → x ∈ t