How to write cases in Markdown equations

Question

How can I write something like this in markdown?

Here are the specific things I don't know how to do:

• The big curly brace with two lines
• If it's required after I know the above, the tab separation within the two lines

Here's what I would do if I knew the right syntax:

$$
CE(p, y) = \curlytwo{-\log(p) \tab \text{if }y=1}{-\log(1-p) \tab \text{otherwise.}}
$$

where I've invented \curlytwo and \tab.

Answer 1

You can use the cases environment to write cases which is supported in MathJax:

$$
\mathrm{CE}(p, y) = \begin{cases}
    -\log(p) & \text{if } y = 1 \\ % & is your "\tab"-like command (it's a tab alignment character)
    -\log(1-p) & \text{otherwise.}
\end{cases}
$$