MathJax 的基本运用

Reference:

https://math.meta.stackexchange.com/questions/5020/mathjax-basic-tutorial-and-quick-reference

1、 绝对值和范数（Absolute values and norms）

The absolute value of some expression can be denoted as lvert x vert or, more generally, as leftlvert … ight vert. It renders as $lvert x vert$ .

The norm of a vector (or similar) can be denoted as lVert v Vert or, more generally, as leftlVert … ight Vert. It renders as $lVert v Vert$. (You may also write left|… ight| instead.)

In both cases, the rendering is better than what you'd get from |x| or ||v|| , which render with bars that don't descend low enough and sub-optimal spacing.  $|x|$ or $||v||$.

  

It was typeset as

$$|x|, ||v|| quadlongrightarrowquadlvert x vert, lVert v Vert$$