Theorem cbvoprab3davw

Description: Change the third bound variable in an operation abstraction. Deduction form. (Contributed by GG, 14-Aug-2025)

	Ref	Expression
Hypothesis	cbvoprab3davw.1	⊢ ( ( 𝜑 ∧ 𝑧 = 𝑤 ) → ( 𝜓 ↔ 𝜒 ) )
Assertion	cbvoprab3davw	⊢ ( 𝜑 → { ⟨ ⟨ 𝑥 , 𝑦 ⟩ , 𝑧 ⟩ ∣ 𝜓 } = { ⟨ ⟨ 𝑥 , 𝑦 ⟩ , 𝑤 ⟩ ∣ 𝜒 } )

Proof

Step	Hyp	Ref	Expression
1		cbvoprab3davw.1	⊢ ( ( 𝜑 ∧ 𝑧 = 𝑤 ) → ( 𝜓 ↔ 𝜒 ) )
2		simpr	⊢ ( ( 𝜑 ∧ 𝑧 = 𝑤 ) → 𝑧 = 𝑤 )
3	2	opeq2d	⊢ ( ( 𝜑 ∧ 𝑧 = 𝑤 ) → ⟨ ⟨ 𝑥 , 𝑦 ⟩ , 𝑧 ⟩ = ⟨ ⟨ 𝑥 , 𝑦 ⟩ , 𝑤 ⟩ )
4	3	eqeq2d	⊢ ( ( 𝜑 ∧ 𝑧 = 𝑤 ) → ( 𝑡 = ⟨ ⟨ 𝑥 , 𝑦 ⟩ , 𝑧 ⟩ ↔ 𝑡 = ⟨ ⟨ 𝑥 , 𝑦 ⟩ , 𝑤 ⟩ ) )
5	4 1	anbi12d	⊢ ( ( 𝜑 ∧ 𝑧 = 𝑤 ) → ( ( 𝑡 = ⟨ ⟨ 𝑥 , 𝑦 ⟩ , 𝑧 ⟩ ∧ 𝜓 ) ↔ ( 𝑡 = ⟨ ⟨ 𝑥 , 𝑦 ⟩ , 𝑤 ⟩ ∧ 𝜒 ) ) )
6	5	cbvexdvaw	⊢ ( 𝜑 → ( ∃ 𝑧 ( 𝑡 = ⟨ ⟨ 𝑥 , 𝑦 ⟩ , 𝑧 ⟩ ∧ 𝜓 ) ↔ ∃ 𝑤 ( 𝑡 = ⟨ ⟨ 𝑥 , 𝑦 ⟩ , 𝑤 ⟩ ∧ 𝜒 ) ) )
7	6	2exbidv	⊢ ( 𝜑 → ( ∃ 𝑥 ∃ 𝑦 ∃ 𝑧 ( 𝑡 = ⟨ ⟨ 𝑥 , 𝑦 ⟩ , 𝑧 ⟩ ∧ 𝜓 ) ↔ ∃ 𝑥 ∃ 𝑦 ∃ 𝑤 ( 𝑡 = ⟨ ⟨ 𝑥 , 𝑦 ⟩ , 𝑤 ⟩ ∧ 𝜒 ) ) )
8	7	abbidv	⊢ ( 𝜑 → { 𝑡 ∣ ∃ 𝑥 ∃ 𝑦 ∃ 𝑧 ( 𝑡 = ⟨ ⟨ 𝑥 , 𝑦 ⟩ , 𝑧 ⟩ ∧ 𝜓 ) } = { 𝑡 ∣ ∃ 𝑥 ∃ 𝑦 ∃ 𝑤 ( 𝑡 = ⟨ ⟨ 𝑥 , 𝑦 ⟩ , 𝑤 ⟩ ∧ 𝜒 ) } )
9		df-oprab	⊢ { ⟨ ⟨ 𝑥 , 𝑦 ⟩ , 𝑧 ⟩ ∣ 𝜓 } = { 𝑡 ∣ ∃ 𝑥 ∃ 𝑦 ∃ 𝑧 ( 𝑡 = ⟨ ⟨ 𝑥 , 𝑦 ⟩ , 𝑧 ⟩ ∧ 𝜓 ) }
10		df-oprab	⊢ { ⟨ ⟨ 𝑥 , 𝑦 ⟩ , 𝑤 ⟩ ∣ 𝜒 } = { 𝑡 ∣ ∃ 𝑥 ∃ 𝑦 ∃ 𝑤 ( 𝑡 = ⟨ ⟨ 𝑥 , 𝑦 ⟩ , 𝑤 ⟩ ∧ 𝜒 ) }
11	8 9 10	3eqtr4g	⊢ ( 𝜑 → { ⟨ ⟨ 𝑥 , 𝑦 ⟩ , 𝑧 ⟩ ∣ 𝜓 } = { ⟨ ⟨ 𝑥 , 𝑦 ⟩ , 𝑤 ⟩ ∣ 𝜒 } )