Metamath Proof Explorer


Theorem ssrab3

Description: Subclass relation for a restricted class abstraction. (Contributed by Jonathan Ben-Naim, 3-Jun-2011)

Ref Expression
Hypothesis ssrab3.1 B = x A | φ
Assertion ssrab3 B A

Proof

Step Hyp Ref Expression
1 ssrab3.1 B = x A | φ
2 ssrab2 x A | φ A
3 1 2 eqsstri B A