atan2(3F)

NAME
     atan2, datan2, qatan2, atan2d, datan2d, qatan2d - FORTRAN arctangent
     intrinsic function

SYNOPSIS
     real r1, r2, r3
     double precision dp1, dp2, dp3
     real*16 qp1, qp2, qp3
     real*4 r4, r5, r6
     real*8 dp4, dp5, dp6
     real*16 qp4, qp5, qp6

     r3 = atan2(r1, r2)

     dp3 = datan2(dp1, dp2)
     dp3 = atan2(dp1, dp2)

     qp3 = qatan2(qp1, qp2)
     qp3 = atan2(qp1, qp2)

     r6 = atan2d(r4, r5)

     dp6 = datan2d(dp4, dp5)
     dp6 = atan2d(dp4, dp5)

     qp6 = qatan2d(qp4, qp5)
     qp6 = atan2d(qp4, qp5)

DESCRIPTION
     atan2 returns the arctangent of arg1/arg2 as a real value.  datan2
     returns the double-precision arctangent of its double-precision
     arguments.  qatan2 returns the real*16 arctangent of its real*16
     arguments.  The generic form atan2 may be used with impunity with
     double-precision or real*16 arguments.  If the value of the first
     argument of atan2, datan2, or qatan2 is positive, the result is positive.
     If the value of the first argument is negative, the result is negative.
     When the value of the first argument is positive/negative zero, the
     result is positive/negative zero if the second argument is positive and
     positive/negative Pi if the second argument is negative.  If the value of
     the second argument is zero, the absolute value of the result is Pi/2.
     Both arguments must not have the value zero.  The result of atan2,
     datan2, and qatan2 is in radians and is in the range: -Pi <= result <=
     Pi.

     atan2d returns the arctangent of arg1/arg2 as a real*4 value.  datan2d
     returns the real*8 arctangent of its real*8 arguments.  qatan2d returns
     the real*16 arctangent of its real*16 arguments.  The generic form atan2d
     may be used with impunity with real*8 or real*16 arguments.  If the value
     of the first argument of atan2d, datan2d, or qatan2d is positive, the
     result is positive.  When the value of the first argument is zero, the
     result is zero if the second argument is positive and 180.0 if the second
     argument is negative.  If the value of the first argument is negative,
     the result is negative.  If the value of the second argument is zero, the
     absolute value of the result is 90.0 .  Both arguments must not have the
     value zero.  The result of atan2d, datan2d, and qdatan2d is in degrees
     and is in the range: -180 degrees <= result <= 180 degrees.

SEE ALSO
     trig(3M).