Theorem idn3

Description: Virtual deduction identity rule for three virtual hypotheses. (Contributed by Alan Sare, 11-Jun-2011) (Proof modification is discouraged.) (New usage is discouraged.)

	Ref	Expression
Assertion	idn3	⊢ (    𝜑    ,    𝜓    ,    𝜒    ▶    𝜒    )

Proof

Step	Hyp	Ref	Expression
1		idd	⊢ ( 𝜓 → ( 𝜒 → 𝜒 ) )
2	1	a1i	⊢ ( 𝜑 → ( 𝜓 → ( 𝜒 → 𝜒 ) ) )
3	2	dfvd3ir	⊢ (    𝜑    ,    𝜓    ,    𝜒    ▶    𝜒    )