atan()                   Calculate Arc Tangent
 
 #include <math.h>
 
 double     atan(x);                     arc tangent value (in radians)
 double     x;                           tangent value
 
    atan() returns the arc tangent of 'x' in radians.  The return value
    will be in the range -pi/2 to pi/2.  All values of 'x' are legal.
 
    Returns:    Arc tangent of 'x'.
 
      Notes:    atan() does not return any errors.
 
  -------------------------------- Example ---------------------------------
 
    The following statements print the arc tangent of -1.0.
 
         #include <math.h>        /* Required for function definition only */
         #include <stdio.h>       /* for printf() */
 
         main()
         {
             double arc_tan;
 
             arc_tan = atan(-1.0);   /* arc_tan = -pi/4 (-0.7853982) */
             printf("arc tangent of -1 is %.7f radians\n", arc_tan);
         }

Seealso:


 atan2() 
 tan() 
 matherr()