57b24eb0050596ce5e114e7292695d896672bb93
* Copyright (c) 1987 Regents of the University of California.
* Redistribution and use in source and binary forms are permitted
* provided that this notice is preserved and that due credit is given
* to the University of California at Berkeley. The name of the University
* may not be used to endorse or promote products derived from this
* software without specific prior written permission. This software
* is provided ``as is'' without express or implied warranty.
* All recipients should regard themselves as participants in an ongoing
* research project and hence should feel obligated to report their
* experiences (good or bad) with these elementary function codes, using
* the sendbug(8) program, to the authors.
static char sccsid
[] = "@(#)tan.c 5.2 (Berkeley) %G%";
if(!finite(x
)) /* tan(NaN) and tan(INF) must be NaN */
x
= drem(x
,PI
); /* reduce x into [-PI/2, PI/2] */
a
= copysign(x
,one
); /* ... = abs(x) */
z
*= half
; /* Next get c = cos(x) accurately */
c
= (z
>= thresh
? half
-((z
-half
)-cc
) : one
-(z
-cc
));
return x
+(x
*(z
-(cc
-ss
)))/c
; /* ... sin/cos */
return copysign(fmax
,x
); /* no inf on 32k */
return c
/(x
+x
*ss
); /* ... cos/sin */