ACOS()
 Computes the cosine arc
------------------------------------------------------------------------------
 Syntax

     ACOS(<nCosine>) --> nCosArc

 Argument

     <nCosine>  Designates the cosine value for an angle where the
     response is determined in radians.  The value is in the range of -1 to
     +1 (inclusive).

 Returns

     ACOS() returns the cosine arc for <nCosine>.

 Description

     ACOS() determines an angle size in radians for a cosine value.  The
     returned value is in the range of 0 to pi.

 Note

     .  The precision of the result can be influenced by the SETPREC()
        function.

 Example

     Compute the cosine arc:

     ? STR(ACOS(0.7), 18, 15)      // 0.795398830184144