As title,
想要打出"因为"的数学符号，却不停失败..
已经尝试单独一行 $\because$ ，依旧无法成功，但是删除\because后，
内容是可以成功编辑的。
如图所示：http://imgur.com/YMRABXu
然后复制了下方错误码，google之后还是不知如何解决问题
附上错误码：
$\because $ The control sequence at the end of the top line of your error
message was never \def'ed. If you have misspelled it (e.g., `\hobx'), type
`I' and the correct spelling (e.g., `I\hbox'). Otherwise just continue, and
I'll forget about whatever was undefined.
请问该从哪边去改善这问题呢...QQ