Theorem xorbi12iOLD

Description: Obsolete version of xorbi12i as of 21-Apr-2024. (Contributed by Mario Carneiro, 4-Sep-2016) (Proof modification is discouraged.) (New usage is discouraged.)

	Ref	Expression
Hypotheses	xorbi12.1	⊢ ( 𝜑 ↔ 𝜓 )
	xorbi12.2	⊢ ( 𝜒 ↔ 𝜃 )
Assertion	xorbi12iOLD	⊢ ( ( 𝜑 ⊻ 𝜒 ) ↔ ( 𝜓 ⊻ 𝜃 ) )

Proof

Step	Hyp	Ref	Expression
1		xorbi12.1	⊢ ( 𝜑 ↔ 𝜓 )
2		xorbi12.2	⊢ ( 𝜒 ↔ 𝜃 )
3	1 2	bibi12i	⊢ ( ( 𝜑 ↔ 𝜒 ) ↔ ( 𝜓 ↔ 𝜃 ) )
4	3	notbii	⊢ ( ¬ ( 𝜑 ↔ 𝜒 ) ↔ ¬ ( 𝜓 ↔ 𝜃 ) )
5		df-xor	⊢ ( ( 𝜑 ⊻ 𝜒 ) ↔ ¬ ( 𝜑 ↔ 𝜒 ) )
6		df-xor	⊢ ( ( 𝜓 ⊻ 𝜃 ) ↔ ¬ ( 𝜓 ↔ 𝜃 ) )
7	4 5 6	3bitr4i	⊢ ( ( 𝜑 ⊻ 𝜒 ) ↔ ( 𝜓 ⊻ 𝜃 ) )