Triangle cleanup

[petertseng]

I know examples don't need to be the best code, but

• this was bugging me while I was looking at the example code for triangle: incorrect test in some tracks #231 so I decided to fix it
• even if the code is unabashedly not the best, I say there's still no harm in increasing readability (which I argue this does)

[petertseng]

Strictly speaking this needn't conflict with #232 since they don't touch the same lines but I just tried to merge the two locally and git plays it safe and declares there is a merge conflict (since the edited lines are just one line apart). So if you care about merging both in quick succession you can deal with the conflict in the obvious way. I can deal with the rebase if it's OK to merge them a few hours apart, of course (and I argue that it's totally OK to merge this one later)

[kytrinyx]

This is all good! Thanks for fixing :)