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Diffstat (limited to 'sysdeps/generic/tan.c')
| -rw-r--r-- | sysdeps/generic/tan.c | 74 |
1 files changed, 74 insertions, 0 deletions
diff --git a/sysdeps/generic/tan.c b/sysdeps/generic/tan.c new file mode 100644 index 0000000..61ed5c5 --- /dev/null +++ b/sysdeps/generic/tan.c @@ -0,0 +1,74 @@ +/* + * Copyright (c) 1987, 1993 + * The Regents of the University of California. All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * 3. All advertising materials mentioning features or use of this software + * must display the following acknowledgement: + * This product includes software developed by the University of + * California, Berkeley and its contributors. + * 4. Neither the name of the University nor the names of its contributors + * may be used to endorse or promote products derived from this software + * without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE + * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS + * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY + * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + */ + +#ifndef lint +static char sccsid[] = "@(#)tan.c 8.1 (Berkeley) 6/4/93"; +#endif /* not lint */ + +#include "trig.h" +double +tan(x) +double x; +{ + double a,z,ss,cc,c; + int k; + + if(!finite(x)) /* tan(NaN) and tan(INF) must be NaN */ + return x-x; + x = drem(x,PI); /* reduce x into [-PI/2, PI/2] */ + a = copysign(x,one); /* ... = abs(x) */ + if (a >= PIo4) { + k = 1; + x = copysign(PIo2-a,x); + } + else { + k = 0; + if (a < small) { + big+a; + return x; + } + } + z = x*x; + cc = cos__C(z); + ss = sin__S(z); + z *= half; /* Next get c = cos(x) accurately */ + c = (z >= thresh ? half-((z-half)-cc) : one-(z-cc)); + if (k == 0) + return x+(x*(z-(cc-ss)))/c; /* ... sin/cos */ +#ifdef national + else if (x == zero) + return copysign(fmax,x); /* no inf on 32k */ +#endif /* national */ + else + return c/(x+x*ss); /* ... cos/sin */ +} |