Tan()
tan(<number>[, <units>])
Returns the tangent of <number> where <number> is expressed in <units>. <units> may be 'radians', 'degrees', or 'gradians' or just the first letter of any of these. By default, <units> is radians.
In a circle, there are 2*pi() radians, 360 degrees, and 400 gradians.
Example
> say tan(0)
You say, "0"
> say tan(1)
You say, "1.557408"
> say tan(fdiv(pi(),4))
You say, "1"