functions:trigonometric

ATAN2

 syntax: ATAN2( y,x )  ! arctan of y/x  ( in radians )

 The ATAN2(y,x) function returns the Arc Tangent of y/x, with
 -pi < ATAN2(y,x) <= pi 

 If y > 0, the result is positive. 
 If y = 0, the result is zero if x > 0 and pi if x < 0. 
 If y < 0, the result is negative. If x = 0, the result is -pi/2.

 Both arguments must not have the value zero.

ATAN2D

 syntax: ATAN2D( y,x )  ! arctan of y/x (in degrees)

 The ATAN2D(y,x) function returns the Arc Tangent of y/x, with
 -180 < ATAN2(y,x) <= 180

 If y > 0, the result is positive. 
 If y = 0, the result is zero if x > 0 and pi if x < 0. 
 If y < 0, the result is negative. If x = 0, the result is -90.

 Both arguments must not have the value zero.