document broken inverse trig functions
diff --git a/docs/shading.html b/docs/shading.html
index aa19c88..99342a3 100644
--- a/docs/shading.html
+++ b/docs/shading.html
@@ -45,6 +45,7 @@
 <li>Linking of multiple shaders is not supported
 <li>gl_ClipVertex
 <li>The derivative functions such as dFdx() are not implemented
+<li>The inverse trig functions asin(), acos(), and atan() are not implemented
 </ul>
 
 <p>