ATAN
ATN

Syntax: ATAN (x)
     or ATAN (x,y)      (Minerva and SMS only)
    and ATN (x)         (Math Package)
Location: QL ROM, Math Package

ATAN, is the arc-tangent function, that is to say the inverse of TAN.

TAN ( ATAN ( x )) = x

for all values of x, but due to the fact that TAN works on periods;

 ATAN ( TAN ( x )) = x

is only true for where: -PI/2 < x < PI/2.

A negative angle indicates that the hypotenuse appears below the baseline of the triangle, and it is therefore important to bear in mind the orientation of the screen when using this command.

On Minerva ROMS, ATAN can accept two parameters - ATAN(x,y) will give the angle from the origin to the point (x,y).

This is the same as ATAN(y/x), although no error is given if x=0.

SMS has implemented ATAN similarly to Minerva, although the angle returned is in the range -PI/2...PI/2 instead of 0...PI.

ATN is exactly the same function!!

CROSS-REFERENCE:
TAN, ATN, ATN2 and ARTANH.
