Lemma 32.3.3. Let S be a scheme. Let I be a set and for each i \in I let f_ i : T_ i \to S be an integral morphism. Then the product T = \prod T_ i in the category of schemes over S (Lemma 32.3.1) is integral over S.
Proof. Omitted. Hint: On affine pieces this reduces to the following algebra fact: if A \to B_ i is integral for all i, then A \to \otimes _ A B_ i is integral. \square
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