Metamath Proof Explorer


Theorem nfwe

Description: Bound-variable hypothesis builder for well-orderings. (Contributed by Stefan O'Rear, 20-Jan-2015) (Revised by Mario Carneiro, 14-Oct-2016)

Ref Expression
Hypotheses nffr.r 𝑥 𝑅
nffr.a 𝑥 𝐴
Assertion nfwe 𝑥 𝑅 We 𝐴

Proof

Step Hyp Ref Expression
1 nffr.r 𝑥 𝑅
2 nffr.a 𝑥 𝐴
3 df-we ( 𝑅 We 𝐴 ↔ ( 𝑅 Fr 𝐴𝑅 Or 𝐴 ) )
4 1 2 nffr 𝑥 𝑅 Fr 𝐴
5 1 2 nfso 𝑥 𝑅 Or 𝐴
6 4 5 nfan 𝑥 ( 𝑅 Fr 𝐴𝑅 Or 𝐴 )
7 3 6 nfxfr 𝑥 𝑅 We 𝐴