Theorem equtr

Description: A transitive law for equality. (Contributed by NM, 23-Aug-1993)

	Ref	Expression
Assertion	equtr	|- ( x = y -> ( y = z -> x = z ) )

Proof

Step	Hyp	Ref	Expression
1		ax7	|- ( y = x -> ( y = z -> x = z ) )
2	1	equcoms	|- ( x = y -> ( y = z -> x = z ) )