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.

Christopher had written:

> Okay, why the hell is \chi working, but \Chi isn't?

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.

You can always click the little gear at the upper right of someone's comment to see how they did what they did.