105 lines
2.0 KiB
C
105 lines
2.0 KiB
C
|
|
/* @(#)z_tanf.c 1.0 98/08/13 */
|
|
/******************************************************************
|
|
* The following routines are coded directly from the algorithms
|
|
* and coefficients given in "Software Manual for the Elementary
|
|
* Functions" by William J. Cody, Jr. and William Waite, Prentice
|
|
* Hall, 1980.
|
|
******************************************************************/
|
|
/******************************************************************
|
|
* Tangent
|
|
*
|
|
* Input:
|
|
* x - floating point value
|
|
*
|
|
* Output:
|
|
* tangent of x
|
|
*
|
|
* Description:
|
|
* This routine calculates the tangent of x.
|
|
*
|
|
*****************************************************************/
|
|
|
|
#include "fdlibm.h"
|
|
#include "zmath.h"
|
|
|
|
static const float TWO_OVER_PI = 0.6366197723;
|
|
static const float p[] = { -0.958017723e-1 };
|
|
static const float q[] = { -0.429135777,
|
|
0.971685835e-2 };
|
|
|
|
float
|
|
_DEFUN (tanf, (float),
|
|
float x)
|
|
{
|
|
float y, f, g, XN, xnum, xden, res;
|
|
int N;
|
|
|
|
/* Check for special values. */
|
|
switch (numtestf (x))
|
|
{
|
|
case NAN:
|
|
errno = EDOM;
|
|
return (x);
|
|
case INF:
|
|
errno = EDOM;
|
|
return (z_notanum_f.f);
|
|
}
|
|
|
|
y = fabsf (x);
|
|
|
|
/* Check for values that are out of our range. */
|
|
if (y > 105414357.0)
|
|
{
|
|
errno = ERANGE;
|
|
return (y);
|
|
}
|
|
|
|
if (x < 0.0)
|
|
N = (int) (x * TWO_OVER_PI - 0.5);
|
|
else
|
|
N = (int) (x * TWO_OVER_PI + 0.5);
|
|
|
|
XN = (float) N;
|
|
|
|
f = x - N * __PI_OVER_TWO;
|
|
|
|
/* Check for values that are too small. */
|
|
if (-z_rooteps_f < f && f < z_rooteps_f)
|
|
{
|
|
xnum = f;
|
|
xden = 1.0;
|
|
}
|
|
|
|
/* Calculate the polynomial. */
|
|
else
|
|
{
|
|
g = f * f;
|
|
|
|
xnum = f * (p[0] * g) + f;
|
|
xden = (q[1] * g + q[0]) * g + 1.0;
|
|
}
|
|
|
|
/* Check for odd or even values. */
|
|
if (N & 1)
|
|
{
|
|
xnum = -xnum;
|
|
res = xden / xnum;
|
|
}
|
|
else
|
|
{
|
|
res = xnum / xden;
|
|
}
|
|
|
|
return (res);
|
|
}
|
|
|
|
#ifdef _DOUBLE_IS_32BITS
|
|
|
|
double tan (double x)
|
|
{
|
|
return (double) tanf ((float) x);
|
|
}
|
|
|
|
#endif /* _DOUBLE_IS_32BITS */
|