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theorem Set.mem_of_mem_of_subset

theorem Set.mem_of_mem_of_subset
: ∀ {α : Type u} {x : α} {s t : Set α}, x ∈ s → s ⊆ t → x ∈ t

Published by @sam ·

View source in zpg9xh52

Definitional, with no premises to accept.