14
This question might be a little off-topic for Math Meta—you are likely to get a better response from tex.se. However, since typesetting is often an issue on the main Math SE site, I suppose that this question is also in-scope here.
Don't use \choose. The \choose command is a plain TeX command, and is not really appropriate for use in LaTeX. Instead, use ...
12
You can find several places where this is discussed. The main announcement is Some changes to the profile while we make it responsive (on Meta Stack Exchange). Specifically,
John Omielan's answer is about this issue and contains links to some other places where it was raised/discussed. Also if you browse the linked questions, you can find other related posts ...
7
In the righthand column, click on the "timeline" link:
This brings up the timeline for the given answer. From that timeline, click the link at the top of the page to get to the answer itself:
1
As an alternative, if you're alright with installing userscripts on your browser, you can try one of Samuel Liew's useful userscripts: Post Headers & Question TOC. It provides (among other things) a table of contents of answers in the right sidebar. Clicking on the entry of an answer scrolls the page to the beginning of that answer.
I expect this would ...
1
You can use dcases from mathtools, although I don't know how it works since I tried using the require command and it didn't work. You can find the package and the environment here. For $\rm\LaTeX$ though, it makes the subfunctions render in a displayed style.
Only top voted, non community-wiki answers of a minimum length are eligible