cyclic rings of behavior one
Theorem.
A cyclic ring has a multiplicative identity if and only if it has behavior one.
Proof.
For a proof that a cyclic ring with a multiplicative identity has behavior one, see this theorem (http://planetmath.org/MultiplicativeIdentityOfACyclicRingMustBeAGenerator).
Let be a cyclic ring with behavior one. Let be a generator (http://planetmath.org/Generator) of the additive group
of such that . Let . Then there exists with . Since and multiplication
in cyclic rings is commutative
, then is a multiplicative identity.∎