--- ray/src/common/tcos.c	1998/12/16 18:15:07	3.1
+++ ray/src/common/tcos.c	2013/01/17 22:48:21	3.6
@@ -1,9 +1,6 @@
-/* Copyright (c) 1998 Silicon Graphics, Inc. */
-
 #ifndef lint
-static char SCCSid[] = "$SunId$ SGI";
+static const char	RCSid[] = "$Id: tcos.c,v 3.6 2013/01/17 22:48:21 greg Exp $";
 #endif
-
 /*
  * Table-based cosine approximation.
  *
@@ -11,24 +8,23 @@ static char SCCSid[] = "$SunId$ SGI";
  * to avoid conversion and guarantee that tsin(x)^2 + tcos(x)^2 == 1.
  *
  * No interpolation in this version.
+ *
+ * External symbols declared in rtmath.h
  */
 
+#include "copyright.h"
+
 #include <math.h>
 
+#include "rtmath.h"
+
 #ifndef NCOSENTRY
-#define NCOSENTRY	256
+#define NCOSENTRY	1024
 #endif
 
-#ifdef M_PI
-#define PI		((double)M_PI)
-#else
-#define PI		3.14159265358979323846
-#endif
 
-
 double
-tcos(x)				/* approximate cosine */
-register double	x;
+tcos(double x)				/* approximate cosine */
 {
 	static double	costab[NCOSENTRY+1];
 	register int	i;
@@ -40,8 +36,8 @@ register double	x;
 	if (x < 0.)
 		x = -x;
 	i = (NCOSENTRY*2./PI) * x  +  0.5;
-	if (i >= 4*NCOSENTRY)
-		i %= 4*NCOSENTRY;
+	while (i >= 4*NCOSENTRY)
+		i -= 4*NCOSENTRY;
 	switch (i / NCOSENTRY) {
 	case 0:
 		return(costab[i]);