add directory gnu

gnu/glibc/glibc-1.03/math/bsd/common/tan.c

@@ -0,0 +1,60 @@
+/*
+ * Copyright (c) 1987 Regents of the University of California.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms are permitted provided
+ * that: (1) source distributions retain this entire copyright notice and
+ * comment, and (2) distributions including binaries display the following
+ * acknowledgement:  ``This product includes software developed by the
+ * University of California, Berkeley and its contributors'' in the
+ * documentation or other materials provided with the distribution and in
+ * all advertising materials mentioning features or use of this software.
+ * 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 ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
+ * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
+ */
+
+#ifndef lint
+static char sccsid[] = "@(#)tan.c	5.5 (Berkeley) 10/9/90";
+#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 */
+}