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Metamath Proof Explorer


Theorem inss1

Description: The intersection of two classes is a subset of one of them. Part of Exercise 12 of TakeutiZaring p. 18. (Contributed by NM, 27-Apr-1994)

Ref Expression
Assertion inss1 A B A

Proof

Step Hyp Ref Expression
1 elinel1 x A B x A
2 1 ssriv A B A