Theorem vd23 44622

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 44605	. . 3 ⊢ (𝜑 → (𝜓 → 𝜒))
3	2	a1dd 50	. 2 ⊢ (𝜑 → (𝜓 → (𝜃 → 𝜒)))
4	3	dfvd3ir 44613	1 ⊢ (   𝜑   ,   𝜓   ,   𝜃   ▶   𝜒   )

Syntax hints:  (   wvd2 44597  (   wvd3 44607

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 207  df-an 396  df-3an 1089  df-vd2 44598  df-vd3 44610

This theorem is referenced by:  e23  44775  e32  44778  e123  44782