Theorem e120

Description: A virtual deduction elimination rule. (Contributed by Alan Sare, 10-Jun-2011) (Proof modification is discouraged.) (New usage is discouraged.)

	Ref	Expression
Hypotheses	e120.1	|- (. ph ->. ps ).
	e120.2	|- (. ph ,. ch ->. th ).
	e120.3	|- ta
	e120.4	|- ( ps -> ( th -> ( ta -> et ) ) )
Assertion	e120	|- (. ph ,. ch ->. et ).

Proof

Step	Hyp	Ref	Expression
1		e120.1	|- (. ph ->. ps ).
2		e120.2	|- (. ph ,. ch ->. th ).
3		e120.3	|- ta
4		e120.4	|- ( ps -> ( th -> ( ta -> et ) ) )
5	1	vd12	|- (. ph ,. ch ->. ps ).
6	5 2 3 4	e220	|- (. ph ,. ch ->. et ).