trig(3M)                                                 trig(3M)



     NAME
          sin, cos, tan,  asin,  acos,  atan,  atan2  -  trigonometric
          functions

     SYNOPSIS
          #include <math.h>

          double sin(x)
          double x;

          double cos(x)
          double x;

          double tan(x)
          double x;

          double asin(x)
          double x;

          double acos(x)
          double x;

          double atan(x)
          double x;

          double atan2(y, x)
          double x, y;

     DESCRIPTION
          sin, cos, and tan return, respectively, the sine, cosine,
          and tangent of their argument, which is in radians.

          asin returns the arcsine of x, in the range -π/2 to π/2.

          acos returns the arccosine of x, in the range 0 to π.

          atan returns the arctangent of x, in the range -π/2 to π/2.

          atan2 returns the arctangent of y/x, in the range -π to π,
          using the signs of both arguments to determine the quadrant
          of the return value.

     RETURN VALUE
          sin, cos, and tan lose accuracy when their argument is far
          from zero.  For arguments sufficiently large, these func-
          tions return 0 when there would otherwise be a complete loss
          of significance.  In this case a message indicating TLOSS
          error is printed on the standard error output.  For less ex-
          treme arguments, a PLOSS error is generated but no message
          is printed.  In both cases, errno is set to ERANGE.





     April, 1990                                                     1

     trig(3M)                                                 trig(3M)



          If the magnitude of the argument of asin or acos is greater
          than one, or if both arguments of atan2 are zero, zero is
          returned and errno is set to EDOM.  In addition, a message
          indicating DOMAIN error is printed on the standard error
          output.

          These error-handling procedures may be changed with the
          function matherr(3M).

     SEE ALSO
          matherr(3M).












































     2                                                     April, 1990