amsmathbraket
I am setting questions onto my university's version of Moodle. This accepts LaTeX commands so I can write most maths into a question, however I can only use the preinstalled packages which does not include the braket package, but does include amsmath etc (there isn't exactly a list anywhere).
So is there a way I can write kets when the \ket{} command does not work?
Using the greater than symbol is not really ideal.
Turns out it was two issues at once, which is why I couldn't troubleshoot it myself at first. Initially, it was a typo in the file's local variable declaration (End : instead of End:), which is why it didn't work when I removed my .emacs file. While trying to troubleshoot, I eventually added a couple of lines to the .emacs file, and, because of them, the issue didn't go away when I finally spotted and corrected the typo.
That's also what made me think this wasn't bug, but a standard behavior.
The macros with uppercase initial are "self-expanding" based on the contents, as the documentation says. Just like it's not good to always use \left and \right, it's also good to choose with care between \Bra and \bra.
As far as the additional spacing is concerned, a solution is to load mleftright:
\documentclass{article}
\usepackage{amsmath}
\usepackage{braket,mleftright}
\mleftright
\begin{document}
\begin{align*}
\Bra{\frac{1}{\sqrt{2}}\left(\uparrow + \downarrow\right)}
&=\frac{1}{\sqrt{2}}\left(\Bra{\uparrow}+\Bra{\downarrow}\right)\\
\bra{\frac{1}{\sqrt{2}}\left(\uparrow + \downarrow\right)}
&=\frac{1}{\sqrt{2}}\left(\bra{\uparrow}+\bra{\downarrow}\right)\\
&=2 222 22\\
&=2\mathinner{222}22\\
\end{align*}
\end{document}
Best Answer
It is possible to put the command at the top of the document body, instead of the preamble.
You want the option to specify the size manually, since a bra and its matching ket should always be the same size. If your preamble includes
mathtools, you have an easy way to create new paired delimiters. Otherwise, here's something quick and dirty: