Short and helpful advice on using MathJax on the site ...

Question

The point of this question is to give people a chance to draft their best MathJax tips for new users. Perhaps this question will stand alone as one of the places to go. Perhaps the material in the answers will be edited into an introductory article. Perhaps it will flop. Who knows? But the whole idea is to pool knowledge and experience to help those who are learning.

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Table of Contents:

• Beginner's tutorial (START HERE)
• Dos and don'ts
• Calculus notation

Answer 1

The goal of this post is to outline the absolute basics of how to typeset mathematics using MathJax, without any prior knowledge assumed.

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Introduction: when asking and answering questions, it makes your writing much clearer if you typeset the mathematical notation using the markup language MathJax. Compare how the quadratic formula reads with and without it: $$ \underbrace{x=\frac{-b\pm \sqrt{b^2-4ac}}{2a}}_{\text{With MathJax}} \quad \underbrace{\text{x=-b+-sqrt(b^2-4ac)/2a}}_{\text{Without MathJax}} $$ This tutorial serves as a brief introduction to how MathJax works, and how you can use it. A more comprehensive overview of the subject can be found here.

Table of contents:

1. Getting started
2. Understanding MathJax syntax
3. Numbers and arithmetic
4. Functions
5. Chaining syntax together
6. Miscellaneous commands

1. Getting started: in the body of your post, you can typeset formulas by putting two dollar signs $$ before the formula, and after the formula:

Be careful not to leave an empty line between the formula and the dollar signs. In the above example, the formula is displayed on a new line. This is known as a 'block formula' or 'displayed formula'. It is possible to write out multiple lines of equations. Each time you want to go onto a new line, you have to indicate this by typing two back-slashes \\:

2x + 7 = 15 \\
2x = 8 \\
x = 4

Notice that the final line does not require two back-slashes. If you enclose the above code using dollar signs, then it renders as $$ 2x + 7 = 15 \\ 2x = 8 \\ x = 4 $$ It is also possible to display the formula on the same line as the text:

This is known as an 'inline formula'. Rather than enclosing the formula with two dollar signs, you should only use a single $ at the start and end of the formula. You can also use inline formulas in the title of your post (but not block formulas).

2. Understanding MathJax syntax: since MathJax is a markup language, there is a syntax that you have to follow. Simply enclosing x=-b+-sqrt(b^2-4ac)/2a with dollar signs does not do the trick: $$ x=-b+-sqrt(b^2-4ac)/2a $$ Instead, there are a set of commands that have to followed in order to typeset the equations nicely. The rest of this post will focus on the most common ones; a more comprehensive list can be found in the main tutorial.

In general, if you want to see how a formula was rendered, then right-click on it, and press 'Show Math As', then 'TeX Commands':

If you're wondering how to type a specific symbol, then Detexify is the tool for you. It allows you to draw a symbol, and finds the closest matching command for it. (These commands are not guaranteed to work in MathJax, but they are likely to.)

3. Numbers and arithmetic: to write out equations such as $4+7=11$, you simply have to enclose them using with dollar signs (no special commands are needed). Easy-peasy! 4+7=11 renders as $4+7=11$.

For multiplication and division, there are a number of options:

• $5 \times 7 = 35$ is rendered using 5 \times 7 = 35. If you want to indicate multiplication using a dot, as in $5 \cdot 7 = 35$, you can write 5 \cdot 7 = 35.
• $12 \div 6 = 2$ is rendered using 12 \div 6 = 2. It is more common to indicate division using fractions: $\frac{3x+7}{2}$ is produced by \frac{3x+7}{2}. Notice how the \frac command has to be accompanied by two sets of curly braces. The numerator goes in the first set of curly braces, and the denominator goes in the second set of curly braces. Finally, you can also indicate division simply by using a forward slash: 1/3 produces $1/3$.

For exponents, you have to use a superscript ^. For instance, $2^4=16$ is rendered using 2^4=16. If the exponent has more than one character, then you have to enclose it using curly braces. For instance, $2^{10}=1024$ is rendered using 2^{10}=1024, not 2^10=1024.

Square roots are typeset using the command \sqrt: $\sqrt{64}$ is produced by \sqrt{64}. Confusingly, cube roots can also be typeset using the \sqrt command: $\sqrt[3]{64}$ is produced by \sqrt[3]{64}. $n$-th roots can be handled similarly.

Inequalities such as $5>4$ can be written as 5>4. If you need to use a 'greater than or equal to' sign, then use \geq: $5 \geq 4$ is produced by 5 \geq 4$. The 'less than or equal to' sign is \leq. The 'not equal to' sign is \neq.

4. Functions: to write out a function such as $\sin(x)$, you have to use a backlash: \sin(x). You can also omit the parentheses by using curly braces instead: \sin{x} renders as $\sin{x}$. Alternatively, you can leave a space between the function and the argument: \sin x also renders as $\sin x$. Other functions such as $\ln x$ and $\arctan x$ can be typeset in much the same way. Again, if you are unsure about what the command for a function is, then right-click on it, and press 'Show Math As', then 'TeX Commands'. You can often guess the MathJax command for a function: it is no surprise that \exp renders as $\exp$.

To indicate the base of a logarithm, use an underscore _ and curly braces where needed. \log_{10}x renders as $\log_{10}x$. In general, the subscript of an expression can be typeset with _, and the superscript with ^. For instance, \sin^2 x produces $\sin^2{x}$ and x_1 produces $x_1$. You can even use both a _ and ^ in the same expression: x_1^2 produces $x_1^2$, although this can be written more cleanly using parentheses: (x_1)^2 produces $(x_1)^2$.

Finally, if you want to define a function yourself, then something like f(x)=2x+7 renders as $f(x)=2x+7$.

5. Chaining syntax together: more complicated-looking formulas in MathJax are often built from simpler ones. The formula $$ \frac{1}{x}\sqrt{\frac{1+x}{1-x}}\ln(\frac{2x^2+2x+1}{2x^2-2x+1}) $$ looks unpleasant to typeset, but is actually simply composed of three simple expressions:

\frac{1}{x}
\sqrt{\frac{1+x}{1-x}}
\ln (\frac{2x^2+2x+1}{2x^2-2x+1})

Notice that the MathJax editor has no problem with putting a fraction inside of a square root, for example. One aesthetic issue with the above formula is the odd sizing of the parentheses in $$ \ln(\frac{2x^2+2x+1}{2x^2-2x+1}) $$ This can be remedied by replacing ( with \left( and ) with \right). If we change the code to

\ln\left(\frac{2x^2+2x+1}{2x^2-2x+1}\right)

it displays as $$ \ln\left(\frac{2x^2+2x+1}{2x^2-2x+1}\right) $$ which is more pleasant to look at, though not strictly necessary. If you want to include text in formulas, then use \text. For instance,

\text{speed} = \frac{\text{distance}}{\text{time}}

renders as $$ \text{speed} = \frac{\text{distance}}{\text{time}} $$

6. Miscellaneous commands:

• Greek letters: simply type the name of the Greek letter. \pi renders as $\pi$. If you want uppercase, then begin the command with a capital letter: \Gamma renders as $\Gamma$.
• For set membership, the commands \mathbb and \in come in handy: $x \in \mathbb{R}$ is rendered by x \in \mathbb{R}. The complete list of fonts can be found in the main tutorial.
• For logical implication, \implies and \iff are useful:

$$ x = 5 \implies x^2 = 25 \\ x^2 = 25 \iff x = 5 \text{ or } x = -5 $$ is rendered by

x = 5 \implies x^2 = 25 \\
x^2 = 25 \iff x = 5 \text{ or } x = -5

Answer 2

Some Dos and Don'ts based on a little time in the review queues

Do type each equation inside a single pair of dollar signs $...$, or $$...$$. This is both easier than the alternative, and correct: instead of $x$=$y$+$z$$x$=$y$+$z$, you should write $x=y+z$$x=y+z$.

Do type all mathematics inside Mathjax, even if you don't need a special symbol like $\aleph$ or $\beta$ e.g. $1 = 9 - 8$, instead of 1= 9-8.

Do check the preview to see if what you typed is indeed what you wanted to say!

• If you do not catch the errors, then you may get answers to a question you didn't want to ask.

Do edit your current post to include Mathjax when someone sends you to this page, instead of asking a new question or posting a new answer.

• Also make sure your question (if you are asking one) has context: using Mathjax is not enough to prevent close votes and downvotes.

Don't rely on Unicode characters!

• They don't always 𝕡𝕝𝕒𝕪 𝕟𝕚𝕔𝕖. Mathjax is not only a way to put fancy symbols on the page. Mathjax is easy to read and consistent on any device.

Don't upload pictures of maths that can be easily typed!

• See discussion here. It's more understandable if you are sharing a larger part of a document, but do consider if you really need to share it as less people will read long posts!

Don't use \dfrac,\limits and \displaystyle too often.

• It makes your post messy and unprofessional. If you need to make mathematics on the site appear bigger to you, you can adjust your Mathjax preferences (see instructions here). Also, using them in titles makes them much larger than other titles, which is discouraged.

Answer 3

This answer focuses on calculus notation. I have broken this section off from the beginners tutorial because I'm not convinced that it is essential for new contributors to be aware of the following commands. Personally, I have no issue with a beginner writing "how do I integrate $x^2$" as opposed to "evaluate $\int x^2 \, dx$".

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Calculus notation: this section briefly covers some of the most commonly used notations in calculus, namely series, limits, derivatives, and integrals. To begin with, a series such as the one below can be written using the following commands:

1 + \frac{1}{2} + \frac{1}{3} + \frac{1}{4} + \dots = \infty

$$ 1 + \frac{1}{2} + \frac{1}{3} + \frac{1}{4} + \dots = \infty $$ The above line of code uses the commands \dots and \infty, which are both useful to be aware of. The same series can be written using sigma notation.

\sum_{n=0}^{\infty}\frac{1}{n} = \infty

$$ \sum_{n=1}^{\infty}\frac{1}{n} = \infty $$ This is another example of when you need to use both an underscore _ (for the lower bound) and a superscript ^ (for the upper bound) to properly format the sum. Integrals follow the same pattern:

\int_{0}^{\infty}\frac{\sin x}{x} \, dx = \frac{\pi}{2}

(It's good style to leave a thin space \, between the integrand and the $dx$, but again this is not necessary.) $$ \int_{0}^{\infty}\frac{\sin x}{x} \, dx = \frac{\pi}{2} $$ With both sums and integrals, you can also omit the upper and lower bounds:

\text{mean} = \frac{1}{n}\sum{x_i} \\
\int \sec x \, dx = \log\left|\sec x + \tan x\right|+ C 

$$ \text{mean} = \frac{1}{n}\sum{x_i} \\ \int \sec x \, dx = \log\left|\sec x + \tan x\right|+ C $$ Derivatives are a lot easier to typeset than integrals. Leibnizian notation can be handled using \frac commands:

\frac{dy}{dx} = \frac{dy}{du} \cdot \frac{du}{dx}

$$ \frac{dy}{dx} = \frac{dy}{du} \cdot \frac{du}{dx} $$ Lagrange's prime notation can also be typeset fairly easily:

(f \circ g)'(x) = f'(g(x))g'(x)

The command \circ is sometimes used to indicate the composition of functions: $$ (f \circ g)'(x) = f'(g(x))g'(x) $$ To indicate that one number is approaching number, you can use \to. The sentence 'as $x \to \infty$, $\frac{\ln x}{x} \to 0$' is rendered by

as $x \to \infty$, $\frac{\ln x}{x} \to 0$

Limits can be typeset using \lim and are usually accompanied by an expression that indicates the value that is being approached. Again, you have to use an underscore so that things are positioned correctly.

\lim_{x \to 0}\frac{\sin x}{x}=1

renders as $$ \lim_{x \to 0}\frac{\sin x}{x}=1 $$