How can I use MathJax/Latex to typeset equations on this site?

Question

Engineering.SE supports $\LaTeX$ style equation editing via MathJax. However, most of the guides for typesetting equations with $\LaTeX$ are either too limited or too expansive for new users who just want to ask their question. This post will aim to give a simple introduction to the most commonly used features of equation typesetting. Below are also some links to other guides.

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Other Guides

Limited

• Markdown Editing Help: LaTeX
• When should I use math markup?

Expansive

• MathJax basic tutorial and quick reference
• An Introduction to Using TeX in the Harvard Mathematics Department

Answer 1

The Basics

• Inline equations are surrounded by dollar signs; $\sin(x)$ gives $\sin(x)$.

• Equations on their own line are surrounded by double dollar signs; $$\tan(\theta)=o/a$$ gives $$\tan(\theta)=o/a$$

• Subscripts and superscripts are denoted by the _ and ^ operators; E_i^2 gives $E_i^2$

• Brackets can be used to extend the influence of operators over multiple characters; E_{1,2}^{op} gives $E_{1,2}^{op}$

• Fractions can be made with the \frac{}{} command; \frac{\partial E}{\partial z} gives $\frac{\partial E}{\partial z}$. If your inline fraction is compressed into too small a space, try using \dfrac to force the fraction to display as if it were on its own line; \dfrac{\partial E}{\partial z} gives $\dfrac{\partial E}{\partial z}$.

• Spaces and carriage returns have no meaning; \alpha\beta \gamma gives $\alpha\beta \gamma$

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Common Symbols

Common symbols such as Greek letters are generally rendered by a slash followed by the name. For symbols with both an uppercase and lowercase form the case of the first letter determines the case of the symbol.

• Greek letters (lower): \alpha \beta \gamma \delta \epsilon \zeta \eta \theta \iota \kappa \lambda \mu \nu \xi \omicron \pi \rho \sigma \tau \upsilon \phi \chi \psi \omega gives $\alpha\beta\gamma\delta\epsilon\zeta\eta\theta\iota\kappa\lambda\mu\nu\xi\omicron\pi\rho\sigma\tau\upsilon\phi\chi\psi\omega$

• Greek letters (upper): \Gamma \Delta \Theta \Lambda \Xi \Pi \Sigma \Upsilon \Phi \Psi \Omega gives $\Gamma \Delta \Theta \Lambda \Xi \Pi \Sigma \Upsilon \Phi \Psi \Omega$. Other uppercase Greek letters can be made by simply typing the corresponding letter in the Latin alphabet, e.g. A for upper case alpha.

• Basic Integrals: use \int where limits are added with the superscript and subscript operators; \int_a^b xdx gives $\int_a^b xdx$.

• Multiple Integrals: use \iint and \iiint for double and triple integrals when you don't need to specify separate limits; \iint_A f(x, y) dxdy gives $\iint_A f(x, y) dxdy$

• Pretty Integrals: optionally, use \limits to position the limits of an integral directly above and below the integral symbol and \, to separate terms like $dx$ and $dy$ from the function and each other; \int\limits_a^b\int\limits_c^d f(x,y)\,dx\,dy gives $\int\limits_a^b\int\limits_c^d f(x,y)\,dx\,dy$

• Radicals: use \sqrt{} which will expand to the size of its argument; \sqrt{a} gives $\sqrt{a}$, \sqrt{\frac{a}{b}} gives $\sqrt{\frac{a}{b}}$, etc.

• Relations: \lt \gt \leq \geq \neq gives $\lt\gt\leq\geq\neq$

• Operators: \times \div \pm \mp \cdot gives $\times\div\pm\mp\cdot$

• Approximately: \approx \sim \simeq \propto gives $\approx \sim \simeq \propto$

• Special: \infty \nabla \partial \Im \Re gives $\infty \nabla \partial \Im \Re$

• Special Functions: \sin \cos \exp \ln \log gives $\sin \cos \exp \ln \log$

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Parentheses

• Ordinary parentheses, brackets, and curly braces are added with the symbols ( ) [ ] | | \{ \} (which gives $( ) [ ] | | \{ \}$). Note that the curly braces needs the \ since it is otherwise a special LaTeX symbol.

• Expanding parentheses can be added with the \left and \right commands; \exp [ \sin ( \frac{a}{b} ) ] gives $$\exp [ \sin ( \frac{a}{b} ) ]$$ while \exp \left[ \sin \left( \frac{a}{b} \right) \right] gives $$\exp \left[ \sin \left( \frac{a}{b} \right) \right]$$

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Formatting Tips

• Newlines are ignored unless escaped with \\. For example:

  $$1
  2
  3$$

  $$1 2 3$$

  Versus:

   $$1\\
  2\\
  3$$

  $$1\\ 2\\ 3$$

• Be careful when using the Blockquote button (or CTRL + Q) in the editor window to format MathJax markup; the default behavior is to wrap the quote in a way that can result in undesired angle brackets in the rendered output. Take this formula as an example:

  $$\dfrac {\partial \mathbf u} {\partial t} + \mathbf u \cdot \nabla \mathbf u - \nu \nabla ^2 \mathbf u = - \nabla w + \mathbf g$$

  Highlighting the exact same marked-up formula in the editor window and pressing the Blockquote button produces this output:

  $$\dfrac {\partial \mathbf u} {\partial t} + \mathbf u \cdot \nabla > \mathbf u - \nu \nabla ^2 \mathbf u = - \nabla w + \mathbf g$$

  Notice the extra $>$ that now appears in the second term. To avoid this, make sure to use only a single Blockquote delimiter (>) at the start of the MathJax block ($ or $$).

• Sometimes it's more effective to consolidate several formulas or equations into a single block of MathJax-formatted text than to scatter them throughout the body of a post. In these cases, you can use \tag{} to number or label a block of MathJax markup for later reference:

  $\tag{1} C = 2 \pi r$ $\tag{2} A = \pi r^2$ $\tag{3} V = {4 \over 3} \pi r^3$

  A more detailed explanation, including labeled hyperlink references, is available here on Math.SE.