Mention that the axis in AngleAxis have to be normalized.
diff --git a/doc/C08_TutorialGeometry.dox b/doc/C08_TutorialGeometry.dox
index 452abda..5657dee 100644
--- a/doc/C08_TutorialGeometry.dox
+++ b/doc/C08_TutorialGeometry.dox
@@ -45,7 +45,8 @@
Rotation2D<float> rot2(angle_in_radian);\endcode</td></tr>
<tr class="alt"><td>
3D rotation as an \ref AngleAxis "angle + axis"</td><td>\code
-AngleAxis<float> aa(angle_in_radian, Vector3f(ax,ay,az));\endcode</td></tr>
+AngleAxis<float> aa(angle_in_radian, Vector3f(ax,ay,az));\endcode
+<span class="note">The axis vector must be normalized.</span></td></tr>
<tr><td>
3D rotation as a \ref Quaternion "quaternion"</td><td>\code
Quaternion<float> q; q = AngleAxis<float>(angle_in_radian, axis);\endcode</td></tr>