--- ray/src/px/ra_skel.c	1992/12/17 15:50:13	2.4
+++ ray/src/px/ra_skel.c	1993/06/04 14:47:53	2.5
@@ -19,6 +19,7 @@ static char SCCSid[] = "$SunId$ LBL";
  */
 
 #include  <stdio.h>
+#include  <math.h>
 #ifdef MSDOS
 #include  <fcntl.h>
 #endif