Metamath Proof Explorer


Theorem nfcrd

Description: Consequence of the not-free predicate. (Contributed by Mario Carneiro, 11-Aug-2016)

Ref Expression
Hypothesis nfcrd.1 φ_xA
Assertion nfcrd φxyA

Proof

Step Hyp Ref Expression
1 nfcrd.1 φ_xA
2 nfcr _xAxyA
3 1 2 syl φxyA