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@@ -0,0 +1,122 @@
+//===========================================================================
+//
+//      s_tan.c
+//
+//      Part of the standard mathematical function library
+//
+//===========================================================================
+//####COPYRIGHTBEGIN####
+//
+// -------------------------------------------
+// The contents of this file are subject to the Cygnus eCos Public License
+// Version 1.0 (the "License"); you may not use this file except in
+// compliance with the License.  You may obtain a copy of the License at
+// http://sourceware.cygnus.com/ecos
+// 
+// Software distributed under the License is distributed on an "AS IS"
+// basis, WITHOUT WARRANTY OF ANY KIND, either express or implied.  See the
+// License for the specific language governing rights and limitations under
+// the License.
+// 
+// The Original Code is eCos - Embedded Cygnus Operating System, released
+// September 30, 1998.
+// 
+// The Initial Developer of the Original Code is Cygnus.  Portions created
+// by Cygnus are Copyright (C) 1998 Cygnus Solutions.  All Rights Reserved.
+// -------------------------------------------
+//
+//####COPYRIGHTEND####
+//===========================================================================
+//#####DESCRIPTIONBEGIN####
+//
+// Author(s):   jlarmour@cygnus.co.uk
+// Contributors:  jlarmour@cygnus.co.uk
+// Date:        1998-02-13
+// Purpose:     
+// Description: 
+// Usage:       
+//
+//####DESCRIPTIONEND####
+//
+//===========================================================================
+
+// CONFIGURATION
+
+#include <pkgconf/libm.h>   // Configuration header
+
+// Include the Math library?
+#ifdef CYGPKG_LIBM     
+
+// Derived from code with the following copyright
+
+
+/* @(#)s_tan.c 1.3 95/01/18 */
+/*
+ * ====================================================
+ * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+ *
+ * Developed at SunSoft, a Sun Microsystems, Inc. business.
+ * Permission to use, copy, modify, and distribute this
+ * software is freely granted, provided that this notice 
+ * is preserved.
+ * ====================================================
+ */
+
+/* tan(x)
+ * Return tangent function of x.
+ *
+ * kernel function:
+ *      __kernel_tan            ... tangent function on [-pi/4,pi/4]
+ *      __ieee754_rem_pio2      ... argument reduction routine
+ *
+ * Method.
+ *      Let S,C and T denote the sin, cos and tan respectively on 
+ *      [-PI/4, +PI/4]. Reduce the argument x to y1+y2 = x-k*pi/2 
+ *      in [-pi/4 , +pi/4], and let n = k mod 4.
+ *      We have
+ *
+ *          n        sin(x)      cos(x)        tan(x)
+ *     ----------------------------------------------------------
+ *          0          S           C             T
+ *          1          C          -S            -1/T
+ *          2         -S          -C             T
+ *          3         -C           S            -1/T
+ *     ----------------------------------------------------------
+ *
+ * Special cases:
+ *      Let trig be any of sin, cos, or tan.
+ *      trig(+-INF)  is NaN, with signals;
+ *      trig(NaN)    is that NaN;
+ *
+ * Accuracy:
+ *      TRIG(x) returns trig(x) nearly rounded 
+ */
+
+#include "mathincl/fdlibm.h"
+
+        double tan(double x)
+{
+        double y[2],z=0.0;
+        int n, ix;
+
+    /* High word of x. */
+        ix = CYG_LIBM_HI(x);
+
+    /* |x| ~< pi/4 */
+        ix &= 0x7fffffff;
+        if(ix <= 0x3fe921fb) return __kernel_tan(x,z,1);
+
+    /* tan(Inf or NaN) is NaN */
+        else if (ix>=0x7ff00000) return x-x;            /* NaN */
+
+    /* argument reduction needed */
+        else {
+            n = __ieee754_rem_pio2(x,y);
+            return __kernel_tan(y[0],y[1],1-((n&1)<<1)); /*   1 -- n even
+                                                        -1 -- n odd */
+        }
+}
+
+#endif // ifdef CYGPKG_LIBM     
+
+// EOF s_tan.c