What is the largest m such that there exist $v_1,\dots,v_m \in \mathbb{R}^n$ such that for all $i$ and $j$, if $1\leq i< j\leq m$, then $v_i \cdot v_j < 0$.

Also, the preview screen is not displaying set braces for LaTeX. Is that just the preview, or does it mean the site wouldn't display them after the question had been posted either? (I formatted this question without the braces in case it's the latter.)

`LaTeX block`

and see if that helps? $\endgroup$ – Yemon Choi Jul 11 '10 at 18:09`\{`

and converts it to`{`

, and then jsMath sees`{`

and thinks its just a brace. Another reason for the habit of protecting TeX in backticks is that Markdown and jsMath have very different ideas about what an underscore`_`

means, and can get into conflict. $\endgroup$ – Theo Johnson-Freyd Jul 11 '10 at 18:38