Theorem vd12

Description: A virtual deduction with 1 virtual hypothesis virtually inferring a virtual conclusion infers that the same conclusion is virtually inferred by the same virtual hypothesis and an additional hypothesis. (Contributed by Alan Sare, 12-Jun-2011) (Proof modification is discouraged.) (New usage is discouraged.)

	Ref	Expression
Hypothesis	vd12.1	⊢ (    𝜑    ▶    𝜓    )
Assertion	vd12	⊢ (    𝜑    ,    𝜒    ▶    𝜓    )

Proof

Step	Hyp	Ref	Expression
1		vd12.1	⊢ (    𝜑    ▶    𝜓    )
2	1	in1	⊢ ( 𝜑 → 𝜓 )
3	2	a1d	⊢ ( 𝜑 → ( 𝜒 → 𝜓 ) )
4	3	dfvd2ir	⊢ (    𝜑    ,    𝜒    ▶    𝜓    )