History of Identity element

	Revision 2 . . September 7, 2001 10:05 pm by Zundark [define "inverse"]
	Revision 1 . . September 5, 2001 2:47 am by Zundark [new article]

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Added: 8a9,10

If e is an identity of (S, *) and a * b = e, then a is called a left inverse of b and b is called a right inverse of a. If an element x is both a left inverse and a right inverse of y, then x is called an inverse of y.