TRIG(3M)                 DOMAIN/IX SYS5                  TRIG(3M)



NAME
     sin, cos, tan, asin, acos, atan, atan2 - trigonometric func-
     tions

USAGE
     #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 y, x;


DESCRIPTION
     Sin, cos and tan return respectively the sine, cosine and
     tangent of their argument, x, measured 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.

DIAGNOSTICS
     Sin, cos, and tan lose accuracy when their argument is far
     from zero.  For arguments sufficiently large, these func-
     tions return zero 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 extreme arguments causing partial loss of significance,



Printed 12/4/86                                            TRIG-1

TRIG(3M)                 DOMAIN/IX SYS5                  TRIG(3M)



     a PLOSS error is generated but no message is printed.  In
     both cases, errno is set to ERANGE .

     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).

NOTE
     User programs that call these routines but do not link with
     libm.a will, instead, reference older routines included in
     /lib/clib.  Support for the old (in clib) routines will be
     discontinued in a future release.  See intro(3M).

RELATED INFORMATION
     matherr(3M)

































TRIG-2                                            Printed 12/4/86