Theorem e1bi

Description: Biconditional form of e1a . sylib is e1bi without virtual deductions. (Contributed by Alan Sare, 15-Jun-2011) (Proof modification is discouraged.) (New usage is discouraged.)

	Ref	Expression
Hypotheses	e1bi.1	|- (. ph ->. ps ).
	e1bi.2	|- ( ps <-> ch )
Assertion	e1bi	|- (. ph ->. ch ).

Proof

Step	Hyp	Ref	Expression
1		e1bi.1	|- (. ph ->. ps ).
2		e1bi.2	|- ( ps <-> ch )
3	2	biimpi	|- ( ps -> ch )
4	1 3	e1a	|- (. ph ->. ch ).