atn Function
Purpose:
To return the arc targent of a number.
Syntax:
atn(x) // the returned angle is in the range of -PI/2 through PI/2
atn(x,y) the returned angle is in the range of -PI through PI
Comments:
x must be given in radians.
Example:
print atn(1)
0.7854
p atn(1,2)
0.4636