Metamath Proof Explorer


Theorem mpoxneldm

Description: If the first argument of an operation given by a maps-to rule is not an element of the first component of the domain or the second argument is not an element of the second component of the domain depending on the first argument, then the value of the operation is the empty set. (Contributed by AV, 25-Oct-2020)

Ref Expression
Hypothesis mpoxeldm.f 𝐹 = ( 𝑥𝐶 , 𝑦𝐷𝑅 )
Assertion mpoxneldm ( ( 𝑋𝐶𝑌 𝑋 / 𝑥 𝐷 ) → ( 𝑋 𝐹 𝑌 ) = ∅ )

Proof

Step Hyp Ref Expression
1 mpoxeldm.f 𝐹 = ( 𝑥𝐶 , 𝑦𝐷𝑅 )
2 df-nel ( 𝑋𝐶 ↔ ¬ 𝑋𝐶 )
3 df-nel ( 𝑌 𝑋 / 𝑥 𝐷 ↔ ¬ 𝑌 𝑋 / 𝑥 𝐷 )
4 2 3 orbi12i ( ( 𝑋𝐶𝑌 𝑋 / 𝑥 𝐷 ) ↔ ( ¬ 𝑋𝐶 ∨ ¬ 𝑌 𝑋 / 𝑥 𝐷 ) )
5 ianor ( ¬ ( 𝑋𝐶𝑌 𝑋 / 𝑥 𝐷 ) ↔ ( ¬ 𝑋𝐶 ∨ ¬ 𝑌 𝑋 / 𝑥 𝐷 ) )
6 4 5 bitr4i ( ( 𝑋𝐶𝑌 𝑋 / 𝑥 𝐷 ) ↔ ¬ ( 𝑋𝐶𝑌 𝑋 / 𝑥 𝐷 ) )
7 neq0 ( ¬ ( 𝑋 𝐹 𝑌 ) = ∅ ↔ ∃ 𝑛 𝑛 ∈ ( 𝑋 𝐹 𝑌 ) )
8 1 mpoxeldm ( 𝑛 ∈ ( 𝑋 𝐹 𝑌 ) → ( 𝑋𝐶𝑌 𝑋 / 𝑥 𝐷 ) )
9 8 exlimiv ( ∃ 𝑛 𝑛 ∈ ( 𝑋 𝐹 𝑌 ) → ( 𝑋𝐶𝑌 𝑋 / 𝑥 𝐷 ) )
10 7 9 sylbi ( ¬ ( 𝑋 𝐹 𝑌 ) = ∅ → ( 𝑋𝐶𝑌 𝑋 / 𝑥 𝐷 ) )
11 10 con1i ( ¬ ( 𝑋𝐶𝑌 𝑋 / 𝑥 𝐷 ) → ( 𝑋 𝐹 𝑌 ) = ∅ )
12 6 11 sylbi ( ( 𝑋𝐶𝑌 𝑋 / 𝑥 𝐷 ) → ( 𝑋 𝐹 𝑌 ) = ∅ )