acos(3I)

NAME
     ACOS, DACOS, QACOS, ACOSD, DACOSD, QACOSD - Computes arc cosine
     (inverse cosine)

SYNOPSIS
     ACOS ([X=]x)
     DACOS ([X=]x)
     QACOS ([X=]x)

     ACOSD ([X=]x)
     DACOSD ([X=]x)
     QACOSD ([X=]x)

IMPLEMENTATION
     UNICOS, UNICOS/mk, IRIX systems

     CF90, MIPSpro 7 Fortran 90, MIPSpro Fortran 77

STANDARDS
     Fortran

     Fortran extensions:  QACOS, ACOSD, DACOSD, QACOSD

DESCRIPTION
     ACOS, DACOS, and QACOS return the arc cosine in radians.  ACOSD,
     DACOSD, and QACOSD return the arc cosine in degrees.  ACOS and ACOSD
     are generic function names; the others are specifics.  These are
     elemental intrinsic functions.  These routines accept the following
     argument:

     x         Must be of type single precision, double precision, or quad
               precision.  The type and kind type of x is identical to the
               type and kind type of the return value.  The absolute value
               of the arguments for ACOS, DACOS, QACOS, ACOSD, DACOSD, and
               QACOSD must be <= 1.  See the RETURN VALUES section for
               information on input data types and return values.

               The data type and kind type for single-precision,
               double-precision, and quad-precision values differ depending
               on your platform.  For platform-specific information, see
               the TERMINOLOGY section of the INTRO_INTRIN(3I) man page.

     For ACOS, DACOS, and QACOS, the result is in radians and is in the
     range 0 <= result <= pi.  The generic form, ACOS, can be used for all
     real data types because it derives its type and kind type from that of
     its argument.

     For ACOSD, DACOSD, and QACOSD, the result is in degrees and is in the
     range 0 <= result <= 180.  The generic form, ACOSD, can be used for
     all real data types because it derives its type and kind type from
     that of its argument.

     Vector versions of these intrinsics exist on some systems.  Vector
     versions of ACOS and DACOS exist on UNICOS and UNICOS/mk systems.  On
     UNICOS/mk systems, the vector versions of these intrinsics are used
     when -O vector3 or -O3 has been specified on the compiler command
     line.  On UNICOS/mk systems, the 64-bit intrinsic vectorizes; the
     32-bit version does not.  A vector version of the single-precision and
     double-precision ACOS intrinsic exists on IRIX systems and is used
     when -O3 is specified on the compiler command line.

     These functions evaluate y = arccos(x).

NOTES
     The ACOS and DACOS intrinsic function names can be passed as
     arguments; the others cannot.

     On CRAY T90 systems that support IEEE arithmetic, the following return
     value occurs:

               ACOS(x)=NaN if |x| > 1.0 or if x = NaN

RETURN VALUES
     ACOS and ACOSD return the real arc cosine of their real arguments.

     DACOS and DACOSD return the double-precision arc cosine of their
     double-precision arguments.

     QACOS and QACOSD return the quad-precision arc cosine of their
     quad-precision arguments.

SEE ALSO
     intro_intrin(3I)

     Intrinsic Procedures Reference Manual for the printed version of this
     man page.