acos
 facos 

 NAME
  acos    - return arc cosine of a double quantity
  facos   - return arc cosine of a float quantity

 SYNOPSIS
  #include <math.h>

  double a = acos(b);
  double b;

  float  c = facos(d);
  float  d;

 FUNCTION
  Returns the arc cosine of a floating point quantity

 EXAMPLE
  /*
   *  compile with the math library -lm
   */

  #include <math.h>
  #include <stdio.h>

  main()
  {
      {
      double a = acos(0.25);
      printf("acos 0.25 = %lfn", a);     /*  1.318   */
      }
      {                       /*  less accuracy   */
      float a = facos(0.25);
      printf("acos 0.25 = %lfn", (double)a);
      }
      return(0);
  }

 INPUTS
  double b;   double floating point value
  float  d;   float  floating point value

 RESULTS
  double a;   result double floating point value
  float  c;   result float  floating point value