title: HelloThere

This is a TiddlyWiki plugin for mathematical and chemical 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 - mathematical typesetting

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

!! Example 1

If the text between `$$` contains newlines it will rendered in display mode:

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

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

!! Example 2

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

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


!! Example 3

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

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

!! Widget Example

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

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

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

! ''Error Handling''

Any LaTeX syntax errors are flagged with the problematic syntax highlighted. For example:

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

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

<hr>

! Examples - chemical typesetting

These examples are taken from [ext[https://mhchem.github.io/MathJax-mhchem/]]

!! Example 1

```
$$
\ce{CO2 + C -> 2 CO}
$$
```

$$
\ce{CO2 + C -> 2 CO}
$$


!! Example 2

```
$$
\ce{Hg^2+ ->[I-] HgI2 ->[I-] [Hg^{II}I4]^2-}
$$
```

$$
\ce{Hg^2+ ->[I-] HgI2 ->[I-] [Hg^{II}I4]^2-}
$$


!! Example 3

```
$$
\ce{x Na(NH4)HPO4 ->[\Delta] (NaPO3)_x + x NH3 ^ + x H2O}
$$
```

$$
\ce{x Na(NH4)HPO4 ->[\Delta] (NaPO3)_x + x NH3 ^ + x H2O}
$$


!! Example 4

```
$$
\ce{A\bond{~--}B\bond{~=}C\bond{-~-}D}
$$
```

$$
\ce{A\bond{~--}B\bond{~=}C\bond{-~-}D}
$$


!! Example 5

```
$$
\ce{Li^x_{Li,1-2x}Mg^._{Li,x}$V$'_{Li,x}Cl^x_{Cl}}
$$
```

$$
\ce{Li^x_{Li,1-2x}Mg^._{Li,x}$V$'_{Li,x}Cl^x_{Cl}}
$$


!! Example 6

```
$$
\ce{Zn^2+  <=>[+ 2OH-][+ 2H+]  $\underset{\text{amphoteres Hydroxid}}{\ce{Zn(OH)2 v}}$  <=>[+ 2OH-][+ 2H+]  $\underset{\text{Hydroxozikat}}{\ce{[Zn(OH)4]^2-}}$}
$$
```

$$
\ce{Zn^2+  <=>[+ 2OH-][+ 2H+]  $\underset{\text{amphoteres Hydroxid}}{\ce{Zn(OH)2 v}}$  <=>[+ 2OH-][+ 2H+]  $\underset{\text{Hydroxozikat}}{\ce{[Zn(OH)4]^2-}}$}
$$