Kerodon

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4.44
\begin{equation} \begin{gathered}\label{equation:diagram-of-collapse} \xymatrix@R =50pt@C=50pt{ (X \times \{ 0 \} \times Y) \coprod (X \times \{ 1\} \times Y) \ar [r] \ar [d]^{\pi _{X} \coprod \pi _{Y}} & X \times \Delta ^1 \times Y \ar [d]^{c} \\ ( X \times \{ 0\} ) \coprod ( \{ 1\} \times Y ) \ar [r]^-{( \iota _{X}, \iota _{Y} )} & X \star Y} \end{gathered} \end{equation}