diff --git a/lib/grav_tess.h b/lib/grav_tess.h
index 3dbc7e8..1534c15 100644
--- a/lib/grav_tess.h
+++ b/lib/grav_tess.h
@@ -13,27 +13,29 @@ system x->North, y->East, z->Up (away from center of the Earth).
 To maintain the standard convention, only for component gz the z axis is
 inverted, so a positive density results in positive gz.
 
-Example
+Example (Revised by Dr. Yi Zhang at 2021-05-05)
 -------
 
 To calculate the gzz component due to a tesseroid on a regular grid:
 
-    #include <stdio.h>
-    #include "glq.h"r
-    #include "constants.h"
-    #include "grav_tess.h"
+    #include "stdio.h"
+    #include "tess/glq.h"
+    #include "tess/constants.h"
+    #include "tess/grav_tess.h"
 
     int main()
     {
-        TESSEROID tess = {1000, 44, 46, -1, 1, MEAN_EARTH_RADIUS - 100000,
-                          MEAN_EARTH_RADIUS};
+        TESSEROID tess = {1000, -1, 1, 44, 46, MEAN_EARTH_RADIUS - 100000, MEAN_EARTH_RADIUS};
         GLQ *glqlon, *glqlat, *glqr;
-        double lon, lat, r = MEAN_EARTH_RADIUS + 1500000, res;
+        double lon, lat, res, r = MEAN_EARTH_RADIUS + 150000;
         int order = 8;
 
         glqlon = glq_new(order, tess.w, tess.e);
         glqlat = glq_new(order, tess.s, tess.n);
         glqr = glq_new(order, tess.r1, tess.r2);
+        glq_precompute_sincos(glqlon);
+        glq_precompute_sincos(glqlat);
+        glq_precompute_sincos(glqr);
 
         for(lat = 20; lat <= 70; lat += 0.5)
         {