Description: Restricted specialization. (Contributed by FL, 4-Jun-2012) (Proof shortened by Wolf Lammen, 7-Jan-2020)
| Ref | Expression | ||
|---|---|---|---|
| Assertion | rsp2e | ⊢ ( ( 𝑥 ∈ 𝐴 ∧ 𝑦 ∈ 𝐵 ∧ 𝜑 ) → ∃ 𝑥 ∈ 𝐴 ∃ 𝑦 ∈ 𝐵 𝜑 ) | 
| Step | Hyp | Ref | Expression | 
|---|---|---|---|
| 1 | rspe | ⊢ ( ( 𝑦 ∈ 𝐵 ∧ 𝜑 ) → ∃ 𝑦 ∈ 𝐵 𝜑 ) | |
| 2 | rspe | ⊢ ( ( 𝑥 ∈ 𝐴 ∧ ∃ 𝑦 ∈ 𝐵 𝜑 ) → ∃ 𝑥 ∈ 𝐴 ∃ 𝑦 ∈ 𝐵 𝜑 ) | |
| 3 | 1 2 | sylan2 | ⊢ ( ( 𝑥 ∈ 𝐴 ∧ ( 𝑦 ∈ 𝐵 ∧ 𝜑 ) ) → ∃ 𝑥 ∈ 𝐴 ∃ 𝑦 ∈ 𝐵 𝜑 ) | 
| 4 | 3 | 3impb | ⊢ ( ( 𝑥 ∈ 𝐴 ∧ 𝑦 ∈ 𝐵 ∧ 𝜑 ) → ∃ 𝑥 ∈ 𝐴 ∃ 𝑦 ∈ 𝐵 𝜑 ) |