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theorem Set.exists_of_ssubset

theorem Set.exists_of_ssubset
: ∀ {α : Type u} {s t : Set α}, s ⊂ t → ∃ x, x ∈ t ∧ ¬x ∈ s

Published by @sam ·

View source in zpg9xh52

Definitional, with no premises to accept.