Theorem inxpss3

Description: Two ways to say that an intersection with a Cartesian product is a subclass (see also inxpss ). (Contributed by Peter Mazsa, 8-Mar-2019)

	Ref	Expression
Assertion	inxpss3	⊢ ( ∀ 𝑥 ∀ 𝑦 ( 𝑥 ( 𝑅 ∩ ( 𝐴 × 𝐵 ) ) 𝑦 → 𝑥 ( 𝑆 ∩ ( 𝐴 × 𝐵 ) ) 𝑦 ) ↔ ∀ 𝑥 ∈ 𝐴 ∀ 𝑦 ∈ 𝐵 ( 𝑥 𝑅 𝑦 → 𝑥 𝑆 𝑦 ) )

Proof

Step	Hyp	Ref	Expression
1		brinxp2	⊢ ( 𝑥 ( 𝑅 ∩ ( 𝐴 × 𝐵 ) ) 𝑦 ↔ ( ( 𝑥 ∈ 𝐴 ∧ 𝑦 ∈ 𝐵 ) ∧ 𝑥 𝑅 𝑦 ) )
2		brinxp2	⊢ ( 𝑥 ( 𝑆 ∩ ( 𝐴 × 𝐵 ) ) 𝑦 ↔ ( ( 𝑥 ∈ 𝐴 ∧ 𝑦 ∈ 𝐵 ) ∧ 𝑥 𝑆 𝑦 ) )
3	1 2	imbi12i	⊢ ( ( 𝑥 ( 𝑅 ∩ ( 𝐴 × 𝐵 ) ) 𝑦 → 𝑥 ( 𝑆 ∩ ( 𝐴 × 𝐵 ) ) 𝑦 ) ↔ ( ( ( 𝑥 ∈ 𝐴 ∧ 𝑦 ∈ 𝐵 ) ∧ 𝑥 𝑅 𝑦 ) → ( ( 𝑥 ∈ 𝐴 ∧ 𝑦 ∈ 𝐵 ) ∧ 𝑥 𝑆 𝑦 ) ) )
4		imdistan	⊢ ( ( ( 𝑥 ∈ 𝐴 ∧ 𝑦 ∈ 𝐵 ) → ( 𝑥 𝑅 𝑦 → 𝑥 𝑆 𝑦 ) ) ↔ ( ( ( 𝑥 ∈ 𝐴 ∧ 𝑦 ∈ 𝐵 ) ∧ 𝑥 𝑅 𝑦 ) → ( ( 𝑥 ∈ 𝐴 ∧ 𝑦 ∈ 𝐵 ) ∧ 𝑥 𝑆 𝑦 ) ) )
5	3 4	bitr4i	⊢ ( ( 𝑥 ( 𝑅 ∩ ( 𝐴 × 𝐵 ) ) 𝑦 → 𝑥 ( 𝑆 ∩ ( 𝐴 × 𝐵 ) ) 𝑦 ) ↔ ( ( 𝑥 ∈ 𝐴 ∧ 𝑦 ∈ 𝐵 ) → ( 𝑥 𝑅 𝑦 → 𝑥 𝑆 𝑦 ) ) )
6	5	2albii	⊢ ( ∀ 𝑥 ∀ 𝑦 ( 𝑥 ( 𝑅 ∩ ( 𝐴 × 𝐵 ) ) 𝑦 → 𝑥 ( 𝑆 ∩ ( 𝐴 × 𝐵 ) ) 𝑦 ) ↔ ∀ 𝑥 ∀ 𝑦 ( ( 𝑥 ∈ 𝐴 ∧ 𝑦 ∈ 𝐵 ) → ( 𝑥 𝑅 𝑦 → 𝑥 𝑆 𝑦 ) ) )
7		r2al	⊢ ( ∀ 𝑥 ∈ 𝐴 ∀ 𝑦 ∈ 𝐵 ( 𝑥 𝑅 𝑦 → 𝑥 𝑆 𝑦 ) ↔ ∀ 𝑥 ∀ 𝑦 ( ( 𝑥 ∈ 𝐴 ∧ 𝑦 ∈ 𝐵 ) → ( 𝑥 𝑅 𝑦 → 𝑥 𝑆 𝑦 ) ) )
8	6 7	bitr4i	⊢ ( ∀ 𝑥 ∀ 𝑦 ( 𝑥 ( 𝑅 ∩ ( 𝐴 × 𝐵 ) ) 𝑦 → 𝑥 ( 𝑆 ∩ ( 𝐴 × 𝐵 ) ) 𝑦 ) ↔ ∀ 𝑥 ∈ 𝐴 ∀ 𝑦 ∈ 𝐵 ( 𝑥 𝑅 𝑦 → 𝑥 𝑆 𝑦 ) )