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Metamath Proof Explorer


Theorem inabs

Description: Absorption law for intersection. (Contributed by NM, 16-Apr-2006)

Ref Expression
Assertion inabs A A B = A

Proof

Step Hyp Ref Expression
1 ssun1 A A B
2 dfss2 A A B A A B = A
3 1 2 mpbi A A B = A