The FUNCTION function

You declare a custom function using the FUNCTION function. This must be done on a worksheet created from a special custom function template. A custom function template, Custom, is provided in the Custom subdirectory in the Examples archive. If you are going to create a number of custom function sheets you might want to copy the Custom template as one of your standard templates.

You should use FUNCTION in the following way:

FUNCTION(name:text {, parameter_1:text {, parameter_2:text …}})

You must always specify the name of a custom function.

parameter_n are optional data which may be required by your custom function.

The custom function tangent has one parameter, called angle, which is specified to be of type number, so its first line reads:

FUNCTION("tangent", "angle:number")