Section 11,14: ATAN2D

 ATAN2D (real-number, real-number)

 A function that returns the arc tangent of the quotient of the two
 arguments in degrees.  If both arguments are zero, the result is
 undefined.  If the first argument is positive, the result is
 positive.  If the first argument is negative, the result is
 negative.  If the first argument is zero, the result is zero.  If
 the second argument is zero, the absolute value of the result is 90
 degrees.  The value of the argument must be greater than zero.

 +------+---------+----------+------------+-------------+        
 | Args | Generic | Specific |  Argument  | Result Type |
 +------+---------+----------+------------+-------------+
 |   2  | ATAN2D  | ATAN2D   | REAL*4     | REAL*4      |
 |      |         | DATAN2D  | REAL*8     | REAL*8      |
 |      |see note | QATAN2D  | REAL*16    | REAL*16     |
 +------+---------+----------+------------+-------------+

 NOTE: QATAN2D is not available in DEC Fortran.

 The range of the result is -180 degrees < result <= 180 degrees.