Equivalence of Definitions of Polynomial Ring in Multiple Variables

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Theorem

Let $R$ be a commutative ring with unity.


The following definitions of polynomial ring are equivalent in the following sense:

For every two constructions, there exists an $R$-isomorphism which sends indeterminates to indeterminates.



Definition 1: As the monoid ring on a free monoid on a set

Let $R \sqbrk {\family {X_i: i \in I} }$ be the ring of polynomial forms in $\family {X_i: i \in I}$.


The polynomial ring in $I$ indeterminates over $R$ is the ordered triple $\struct {\struct {A, +, \circ}, \iota, \family {X_i: i \in I} }$





Proof



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