# Add short reference for Latex commands

Some users are not familiar with the LaTeX notations, which is perfectly fine, but it would be better if we could refer them to some FAQ/help page that explain the basic commands, in a similar way to the markdown edit-help.

I suggest to add to the editing help page a short summary of basic Latex commands (and possibly provide a link to a more extensive list of commands)

EDIT: found out that it was already requested before, yet unanswered there.

• See also here. – Raphael Mod May 22 '12 at 17:31

You can enclose LaTeX math code in $...$ for inline math, and $$...$$ resp. for indented equations.

MathJax supports essentially the commands native to $$\LaTeX$$ as well as those defined by amsmath and amssymb (with some exceptions in both directions). For a complete list, see the MathJax reference.

I have found these references to be useful:

Aside from that, my personal hints (and what I edit most):

• \mathbb{N} for the natural numbers; similar for other such sets.
• \mathcal{L} for calligraphic letters, e.g. languages
• If you prefer left-aligned non-inline formulae, use $\qquad \displaystyle ...$ (in an own paragraph) instead of $$...$$.
• \operatorname{name} for long operator names (non-italic letters and spacing).
• \mathrm{name} or \mathsf{name} for dedicated names, such as P and NP (non-italic letters).
• Parentheses around big stuff (e.g. fractions) are usually undersized. Use \left( ... \right) (similar for [ resp. ] and { resp. }) to have them adapt their size accordingly.
• Use \to, \iff and \implies instead of \rightarrow, \Leftrightarrow and \Rightarrow where appropriate (i.e. semantically fitting).
• You can define your own macros. They survive across multiple math environments, so take care not to destroy other posts.
• Use \text{...} when using English in formulae.
• Use \dots instead of ....

Be aware that the spoiler tag (!>) does not support multiple lines -- even inside math formulae! You'll have to write all of your formula in one line when using spoiler tags.

### Examples

Let $$a,b \in \mathbb{B}$$ and $$a \leq b$$. Then, $$a + b \geq b$$.

$$\sum\limits_{i=0}^n i = \frac{n(n+1)}{2}$$

$$\qquad\displaystyle \sum_{i=1}^n i = \frac{n(n+1)}{2}$$

$$\lim\limits_{n \to \infty} \frac{1}{n} = 0$$

$$\max_n f(x) = - \min_n (-f(n))$$

$$L = \{ \langle M, w \rangle \mid M \text{ is a TM and } M(w) = 1 \}$$

Quicksort runs in $$O(n\log n)$$ time on average, but in $$O(n^2)$$ time in the worst case.

\begin{align*} a_0 &= 1 \\ a_{n+1} &= 2 \cdot a_n + 3 \end{align*}

$$\chi_S(s) = \begin{cases} 1 &, s \in S \\ 0 &, s \notin S \end{cases}$$

$$\begin{pmatrix} 1 & 2 & 3 \\ 4 & 5 & 6 \\ 7 & 8 & 9 \end{pmatrix}$$

\begin{align*} S &\to (S)S \mid A \mid \varepsilon \\ A &\to aA \mid a \end{align*}


You may use this online graphical tool to create Latex formulas:

http://www.codecogs.com/latex/eqneditor.php