Great solution to Puzzle 90, Matthew and Christopher! Good work! We now see how disastrous the 'co-triangle inequality' \$$d(a,b) + d(b,c) \le d(a,c)\$$ would be.

LaTeX doesn't have \Chi because they believe a capital Greek letter Chi looks just like an X. But you were trying to draw what Matthew was drawing, namely \$$\mathcal{X}\$$, and that's done using \mathcal{X}. Fong and Spivak use the \mathcal font for enriched categories.