title: HelloThere

This is a TiddlyWiki plugin for mathematical typesetting based on KaTeX from Khan Academy.

It is completely self-contained, and doesn't need an Internet connection in order to work. It works both in the browser and under Node.js.

! Installation

To add the plugin to your own TiddlyWiki5, just drag this link to the browser window:

[[$:/plugins/tiddlywiki/katex]]

! Using KaTeX

The usual way to include ~LaTeX is to use `$$`, as shown in the examples below.

The underlying KaTeX widget is provided under the name `<$latex>` and is also available under the alias `<$katex>`. It's better to use the generic `<$latex>` name unless you are running multiple ~LaTeX plugins and wish to specifically target KaTeX.

! Examples

These examples are taken from http://khan.github.io/KaTeX/

!! Example 1

```
$$\displaystyle f(x) = \int_{-\infty}^\infty\hat f(\xi)\,e^{2 \pi i \xi x}\,d\xi$$
```

$$\displaystyle f(x) = \int_{-\infty}^\infty\hat f(\xi)\,e^{2 \pi i \xi x}\,d\xi$$

!! Example 2

```
$$\displaystyle \frac{1}{\Bigl(\sqrt{\phi \sqrt{5}}-\phi\Bigr) e^{\frac25 \pi}} = 1+\frac{e^{-2\pi}} {1+\frac{e^{-4\pi}} {1+\frac{e^{-6\pi}} {1+\frac{e^{-8\pi}} {1+\cdots} } } }$$
```

$$\displaystyle \frac{1}{\Bigl(\sqrt{\phi \sqrt{5}}-\phi\Bigr) e^{\frac25 \pi}} = 1+\frac{e^{-2\pi}} {1+\frac{e^{-4\pi}} {1+\frac{e^{-6\pi}} {1+\frac{e^{-8\pi}} {1+\cdots} } } }$$

!! Example 3

```
$$\displaystyle \left( \sum_{k=1}^n a_k b_k \right)^2 \leq \left( \sum_{k=1}^n a_k^2 \right) \left( \sum_{k=1}^n b_k^2 \right)$$
```

$$\displaystyle \left( \sum_{k=1}^n a_k b_k \right)^2 \leq \left( \sum_{k=1}^n a_k^2 \right) \left( \sum_{k=1}^n b_k^2 \right)$$

!! Example 4

```
$$\displaystyle 1 +  \frac{q^2}{(1-q)}+\frac{q^6}{(1-q)(1-q^2)}+\cdots = \prod_{j=0}^{\infty}\frac{1}{(1-q^{5j+2})(1-q^{5j+3})}, \quad\quad \text{for }\lvert q\rvert<1.$$
```

$$\displaystyle 1 +  \frac{q^2}{(1-q)}+\frac{q^6}{(1-q)(1-q^2)}+\cdots = \prod_{j=0}^{\infty}\frac{1}{(1-q^{5j+2})(1-q^{5j+3})}, \quad\quad \text{for }\lvert q\rvert<1.$$

!! Widget Example

For more flexibility the KaTeX widget can also be used via the full widget syntax:

```
<$latex text="\displaystyle f(x) = \int_{-\infty}^\infty\hat f(\xi)\,e^{2 \pi i \xi x}\,d\xi"></$latex>
```

<$latex text="\displaystyle f(x) = \int_{-\infty}^\infty\hat f(\xi)\,e^{2 \pi i \xi x}\,d\xi"></$latex>

! Error Handling

An warning message is displayed if KaTeX detects a problem with the ~LaTeX syntax. For example:

```
$$\displaystyle f(x) = \int_{-\infty}^\infinity\hat f(\xi)\,e^{2 \pi i \xi x}\,d\xi$$
```

$$\displaystyle f(x) = \int_{-\infty}^\infinity\hat f(\xi)\,e^{2 \pi i \xi x}\,d\xi$$