Theorem entr4i

Description: A chained equinumerosity inference. (Contributed by NM, 25-Sep-2004)

	Ref	Expression
Hypotheses	entr4i.1	|- A ~~ B
	entr4i.2	|- C ~~ B
Assertion	entr4i	|- A ~~ C

Proof

Step	Hyp	Ref	Expression
1		entr4i.1	|- A ~~ B
2		entr4i.2	|- C ~~ B
3	2	ensymi	|- B ~~ C
4	1 3	entri	|- A ~~ C