Theorem inxpss

Description: Two ways to say that an intersection with a Cartesian product is a subclass. (Contributed by Peter Mazsa, 16-Jul-2019)

	Ref	Expression
Assertion	inxpss	⊢ ( ( 𝑅 ∩ ( 𝐴 × 𝐵 ) ) ⊆ 𝑆 ↔ ∀ 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	1	imbi1i	⊢ ( ( 𝑥 ( 𝑅 ∩ ( 𝐴 × 𝐵 ) ) 𝑦 → 𝑥 𝑆 𝑦 ) ↔ ( ( ( 𝑥 ∈ 𝐴 ∧ 𝑦 ∈ 𝐵 ) ∧ 𝑥 𝑅 𝑦 ) → 𝑥 𝑆 𝑦 ) )
3		impexp	⊢ ( ( ( ( 𝑥 ∈ 𝐴 ∧ 𝑦 ∈ 𝐵 ) ∧ 𝑥 𝑅 𝑦 ) → 𝑥 𝑆 𝑦 ) ↔ ( ( 𝑥 ∈ 𝐴 ∧ 𝑦 ∈ 𝐵 ) → ( 𝑥 𝑅 𝑦 → 𝑥 𝑆 𝑦 ) ) )
4	2 3	bitri	⊢ ( ( 𝑥 ( 𝑅 ∩ ( 𝐴 × 𝐵 ) ) 𝑦 → 𝑥 𝑆 𝑦 ) ↔ ( ( 𝑥 ∈ 𝐴 ∧ 𝑦 ∈ 𝐵 ) → ( 𝑥 𝑅 𝑦 → 𝑥 𝑆 𝑦 ) ) )
5	4	2albii	⊢ ( ∀ 𝑥 ∀ 𝑦 ( 𝑥 ( 𝑅 ∩ ( 𝐴 × 𝐵 ) ) 𝑦 → 𝑥 𝑆 𝑦 ) ↔ ∀ 𝑥 ∀ 𝑦 ( ( 𝑥 ∈ 𝐴 ∧ 𝑦 ∈ 𝐵 ) → ( 𝑥 𝑅 𝑦 → 𝑥 𝑆 𝑦 ) ) )
6		relinxp	⊢ Rel ( 𝑅 ∩ ( 𝐴 × 𝐵 ) )
7		ssrel3	⊢ ( Rel ( 𝑅 ∩ ( 𝐴 × 𝐵 ) ) → ( ( 𝑅 ∩ ( 𝐴 × 𝐵 ) ) ⊆ 𝑆 ↔ ∀ 𝑥 ∀ 𝑦 ( 𝑥 ( 𝑅 ∩ ( 𝐴 × 𝐵 ) ) 𝑦 → 𝑥 𝑆 𝑦 ) ) )
8	6 7	ax-mp	⊢ ( ( 𝑅 ∩ ( 𝐴 × 𝐵 ) ) ⊆ 𝑆 ↔ ∀ 𝑥 ∀ 𝑦 ( 𝑥 ( 𝑅 ∩ ( 𝐴 × 𝐵 ) ) 𝑦 → 𝑥 𝑆 𝑦 ) )
9		r2al	⊢ ( ∀ 𝑥 ∈ 𝐴 ∀ 𝑦 ∈ 𝐵 ( 𝑥 𝑅 𝑦 → 𝑥 𝑆 𝑦 ) ↔ ∀ 𝑥 ∀ 𝑦 ( ( 𝑥 ∈ 𝐴 ∧ 𝑦 ∈ 𝐵 ) → ( 𝑥 𝑅 𝑦 → 𝑥 𝑆 𝑦 ) ) )
10	5 8 9	3bitr4i	⊢ ( ( 𝑅 ∩ ( 𝐴 × 𝐵 ) ) ⊆ 𝑆 ↔ ∀ 𝑥 ∈ 𝐴 ∀ 𝑦 ∈ 𝐵 ( 𝑥 𝑅 𝑦 → 𝑥 𝑆 𝑦 ) )