Description

   atan2() computes the angle in the interval [-pi,pi] whose
   arc tangent is y/x radians for x and y in the interval
   [-infinity, +infinity]. The sign of atan2() is the same as the
   sign of y. The atan2(y, x) function is computed as follows, where
   f is the number of fraction bits associated with the data type:

   Value of Input Arguments            Angle Returned

   x = 0 or y/x > 2**(f+1)             pi/2 * (sign y)
   x > 0 and y/x < or = 2**(f+1)       atan(y/x)
   x < 0 and y/x < or = 2**(f+1)       pi * (sign y) + atan(y/x)

   atand2() computes the angle in the interval [-180,180]
   whose arc tangent is y/x degrees for x and y in the interval
   [-infinity, +infinity]. The sign of atand2() is the same as the
   sign of y.


                          Entry-Point Names

   Generic
   Function   Data Type   OpenVMS           Tru64 UNIX
   Name       Required

   atan2      S_FLOAT     math$atan2_s      atan2f
              T_FLOAT     math$atan2_t      atan2
              X_FLOAT     math$atan2_x      atan2l
              F_FLOAT     math$atan2_f
              G_FLOAT     math$atan2_g

   atand2     S_FLOAT     math$atand2_s     atand2f
              T_FLOAT     math$atand2_t     atand2
              X_FLOAT     math$atand2_x     atand2l
              F_FLOAT     math$atand2_f
              G_FLOAT     math$atand2_g