Metamath Proof Explorer


Theorem 4exdistr

Description: Distribution of existential quantifiers in a quadruple conjunction. (Contributed by NM, 9-Mar-1995) (Proof shortened by Wolf Lammen, 20-Jan-2018)

Ref Expression
Assertion 4exdistr ( ∃ 𝑥𝑦𝑧𝑤 ( ( 𝜑𝜓 ) ∧ ( 𝜒𝜃 ) ) ↔ ∃ 𝑥 ( 𝜑 ∧ ∃ 𝑦 ( 𝜓 ∧ ∃ 𝑧 ( 𝜒 ∧ ∃ 𝑤 𝜃 ) ) ) )

Proof

Step Hyp Ref Expression
1 19.42v ( ∃ 𝑤 ( 𝜒𝜃 ) ↔ ( 𝜒 ∧ ∃ 𝑤 𝜃 ) )
2 1 anbi2i ( ( ( 𝜑𝜓 ) ∧ ∃ 𝑤 ( 𝜒𝜃 ) ) ↔ ( ( 𝜑𝜓 ) ∧ ( 𝜒 ∧ ∃ 𝑤 𝜃 ) ) )
3 19.42v ( ∃ 𝑤 ( ( 𝜑𝜓 ) ∧ ( 𝜒𝜃 ) ) ↔ ( ( 𝜑𝜓 ) ∧ ∃ 𝑤 ( 𝜒𝜃 ) ) )
4 df-3an ( ( 𝜑𝜓 ∧ ( 𝜒 ∧ ∃ 𝑤 𝜃 ) ) ↔ ( ( 𝜑𝜓 ) ∧ ( 𝜒 ∧ ∃ 𝑤 𝜃 ) ) )
5 2 3 4 3bitr4i ( ∃ 𝑤 ( ( 𝜑𝜓 ) ∧ ( 𝜒𝜃 ) ) ↔ ( 𝜑𝜓 ∧ ( 𝜒 ∧ ∃ 𝑤 𝜃 ) ) )
6 5 3exbii ( ∃ 𝑥𝑦𝑧𝑤 ( ( 𝜑𝜓 ) ∧ ( 𝜒𝜃 ) ) ↔ ∃ 𝑥𝑦𝑧 ( 𝜑𝜓 ∧ ( 𝜒 ∧ ∃ 𝑤 𝜃 ) ) )
7 3exdistr ( ∃ 𝑥𝑦𝑧 ( 𝜑𝜓 ∧ ( 𝜒 ∧ ∃ 𝑤 𝜃 ) ) ↔ ∃ 𝑥 ( 𝜑 ∧ ∃ 𝑦 ( 𝜓 ∧ ∃ 𝑧 ( 𝜒 ∧ ∃ 𝑤 𝜃 ) ) ) )
8 6 7 bitri ( ∃ 𝑥𝑦𝑧𝑤 ( ( 𝜑𝜓 ) ∧ ( 𝜒𝜃 ) ) ↔ ∃ 𝑥 ( 𝜑 ∧ ∃ 𝑦 ( 𝜓 ∧ ∃ 𝑧 ( 𝜒 ∧ ∃ 𝑤 𝜃 ) ) ) )