# tan function

- num radians

Converts `radians`

to a double and returns the tangent of the value.

The tangent function is equivalent to `sin(radians)/cos(radians)`

and may be
infinite (positive or negative) when `cos(radians)`

is equal to zero.
If `radians`

is not a finite number, the result is NaN.

## Implementation

`external double tan(num radians);`