In: Advanced Math
Let R and S be rings. Denote the operations in R as +R and ·R and the operations in S as +S and ·S
(i) Prove that the cartesian product R × S is a ring, under componentwise addition and multiplication.
(ii) Prove that R × S is a ring with identity if and only if R and S are both rings with identity.
(iii) Prove that R × S is a commutative ring if and only if R and S are both commutative rings.