# Man Page atanp.3m

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## NAME

```     trig_sun, sincos, sind, cosd,  tand,  asind,  acosd,  atand,
atan2d, sincosd, sinp, cosp, tanp, asinp, acosp, atanp, sin-
cosp, sinpi, cospi, tanpi, asinpi, acospi, atanpi,  atan2pi,
sincospi - more trigonometric functions

```

## SYNOPSIS

```     cc [ flag ... ] file ...  -lsunmath -lm [ library ... ]

#include <sunmath.h>

void sincos(double x, double *s, double *c);

double sind(double x);

double cosd(double x);

double tand(double x);

double asind(double x);

double acosd(double x);

double atand(double x);

double atan2d(double y, double x);

void sincosd(double x, double *s, double *c);

double sinpi(double x);

double cospi(double x);

double tanpi(double x);

double asinpi(double x);

double acospi(double x);

double atanpi(double x);

double atan2pi(double y, double x);

void sincospi(double x, double *s, double *c);

double sinp(double x);

double cosp(double x);

double tanp(double x);

double asinp(double x);

double acosp(double x);

double atanp(double x);

void sincosp(double x, double *s, double *c);

```

## DESCRIPTION

```     sincos(x,s,c) allows simultaneous computation of  *s:=sin(x)
and *c:=cos(x).

sind(x), cosd(x), and tand(x) return trigonometric functions
of   degree   arguments.    sind(x):=   sin(x*pi/180).   The
corresponding   inverse   functions    compute    asind(x):=
asin(x)*180/pi.  Similarly atan2d(y,x):= atan2(y,x)*180/pi.

sinpi(x),  cospi(x),  and  tanpi(x)  avoid   range-reduction
issues because their definition sinpi(x):= sin(pi*x) permits
range reduction that is  fast  and  exact  for  all  x.  The
corresponding    inverse   functions   compute   asinpi(x):=
asin(x)/pi.  Similarly atan2pi(y,x):= atan2(y,x)/pi.

sinp(x), cosp(x), and tanp(x) use PI/2, the double precision
approximation  to  pi/2,  in  the argument reduction step to
reduce arguments exceeding PI/4 in magnitude  to  the  range
-PI/4  to PI/4 . The argument reduction step is accomplished
by the fmod function; thus it is much faster than using  the
true  value  of  pi.   The  relation between sinp and sin is
sinp(x):= sin(x*pi/PI).  The corresponding inverse functions
asinp(x):=  asin(x)*PI/pi.   Since  PI/pi  is close to 1, we
simply return asin(x).  The same  applies  to  acosp(x)  and
atanp(x).

```

```     asin(3M), acos(3M), atan(3M), atan2(3M),  cos(3M),  sin(3M),
tan(3M).

```