Theorem vd23 39650

Description: A virtual deduction with 2 virtual hypotheses virtually inferring a virtual conclusion infers that the same conclusion is virtually inferred by the same 2 virtual hypotheses and a third hypothesis. (Contributed by Alan Sare, 12-Jun-2011.) (Proof modification is discouraged.) (New usage is discouraged.)

Hypothesis

Ref	Expression
vd23.1	⊢ (   𝜑   ,   𝜓   ▶   𝜒   )

Assertion

Ref	Expression
vd23	⊢ (   𝜑   ,   𝜓   ,   𝜃   ▶   𝜒   )

Proof of Theorem vd23

Step	Hyp	Ref	Expression
1		vd23.1	. . . 4 ⊢ (   𝜑   ,   𝜓   ▶   𝜒   )
2	1	dfvd2i 39624	. . 3 ⊢ (𝜑 → (𝜓 → 𝜒))
3	2	a1dd 50	. 2 ⊢ (𝜑 → (𝜓 → (𝜃 → 𝜒)))
4	3	dfvd3ir 39632	1 ⊢ (   𝜑   ,   𝜓   ,   𝜃   ▶   𝜒   )

Syntax hints:  (   wvd2 39616  (   wvd3 39626

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8

This theorem depends on definitions:  df-bi 199  df-an 387  df-3an 1113  df-vd2 39617  df-vd3 39629

This theorem is referenced by:  e23  39804  e32  39807  e123  39811