• Functoriality. The assignments
    \[ \webleft (X,x_{0}\webright ),\webleft (Y,y_{0}\webright ),\webleft (\webleft (X,x_{0}\webright ),\webleft (Y,y_{0}\webright )\webright )\mapsto \webleft (X\times Y,\webleft (x_{0},y_{0}\webright )\webright ) \]

    define functors

    \begin{gather*} \begin{aligned} X\times - & \colon \mathsf{Sets}_{*} \to \mathsf{Sets}_{*},\\ -\times Y & \colon \mathsf{Sets}_{*} \to \mathsf{Sets}_{*}, \end{aligned}\\ -_{1}\times -_{2} \colon \mathsf{Sets}_{*}\times \mathsf{Sets}_{*} \to \mathsf{Sets}_{*}, \end{gather*}

    defined in the same way as the functors of Chapter 2: Constructions With Sets, Item 1 of Proposition 2.1.3.1.2.


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