# The TeX input processor — MathJax v1.0 documentation

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# The TeX input processor

The options below control the operation of the TeX input processor that is run when you include `"input/TeX"` in the jax array of your configuration. They are listed with their default values. To set any of these options, include a `TeX` section in your `MathJax.Hub.Config()` call. For example

    MathJax.Hub.Config({
      TeX: {
        Macros: {
          RR: '{\\bf R}',
          bold: ['{\\bf #1}', 1]
        }
      }
    });

would set the `Macros` configuration option to cause two new macros to be defined within the TeX input processor.

`TagSide: "right"`

  This specifies the side on which `\tag{}` macros will place the tags. Set it to `"left"` to place the tags on the left-hand side.

`TagIndent: ".8em"`

  This is the amount of indentation (from the right or left) for the tags produced by the `\tag{}` macro.

`MultLineWidth: "85%"`

  The width to use for the multline environment that is part of the `AMSmath` extension. This width gives room for tags at either side of the equation, but if you are displaying mathematics in a small area or a thin column of text, you might need to change the value to leave sufficient margin for tags.

`Macros: {}`

  This lists macros to define before the TeX input processor begins. These are name:value pairs where the name gives the name of the TeX macro to be defined, and value gives the replacement text for the macro. The value canbe an array of the form [value,n], where value is the replacement text and n is the number of parameters for the macro. Note that since the value is a javascript string, backslashes in the replacement text must be doubled to prevent them from acting as javascript escape characters.

  For example,

      Macros: {
        RR: '{\\bf R}',
        bold: ['{\\bf #1}', 1]
      }

  would ask the TeX processor to define two new macros: `\RR`, which produces a bold-face “R”, and `\bold{...}`, which takes one parameter and set it in the bold-face font.

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