• Proof of Item (b): We may partition the monoidality diagram for $\text{id}^{\otimes }$ of Item 2 of Remark 10.1.1.1.3 as follows:

    Since:

    • Subdiagram (1) commutes by assumption.
    • Subdiagram (2) commutes by assumption.
    • Subdiagram (3) commutes by Item (b) of Item 1.
    it follows that the boundary diagram also commutes, i.e. $\text{id}^{\otimes }$ satisfies the monoidality condition of Item 2 of Remark 10.1.1.1.3.


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