[Bf-docboard-svn] bf-manual: [7366] trunk/blender_docs/manual/advanced/appendices/rotations.rst: Minor addition

[Pep]

Revision: 7366
          https://developer.blender.org/rBM7366
Author:   pepribal
Date:     2020-11-12 09:54:30 +0100 (Thu, 12 Nov 2020)
Log Message:
-----------
Minor addition

Modified Paths:
--------------
    trunk/blender_docs/manual/advanced/appendices/rotations.rst

Modified: trunk/blender_docs/manual/advanced/appendices/rotations.rst
===================================================================
--- trunk/blender_docs/manual/advanced/appendices/rotations.rst	2020-11-11 23:14:39 UTC (rev 7365)
+++ trunk/blender_docs/manual/advanced/appendices/rotations.rst	2020-11-12 08:54:30 UTC (rev 7366)
@@ -105,8 +105,8 @@
 components are called, in Blender, X, Y, Z and W.
 
 When rotating interactively in quaternion mode, the so called norm (length) of the quaternion will remain constant.
-By definition, the norm of a quaternion equals 1.0. When you select the quaternion mode in Blender, the XYZW
-components describe a 1.0 norm quaternion.
+By definition, the norm of a quaternion equals 1.0 (that's a **normalized** quaternion). When you select the
+quaternion mode in Blender, the XYZW components describe a normalized quaternion.
 
 .. note::
 
@@ -135,8 +135,10 @@
 is as follows:
 
 * X, Y and Z mean exactly the same as in axis-angle: they just define an axis around which the rotation takes place.
-* W can be used to retrieve the actual rotation around the defined angle. The following formula applies:
-  :math:`W = \cos(\frac{a}{2})`, where *a* is actually the rotation angle we are looking for. 
+* W can be used to retrieve the actual rotation around the defined angle. The following formula applies (provided
+  that the *quaternion is normalized*):
+  :math:`W = \cos(\frac{a}{2})`, where *a* is actually the rotation angle we are looking for. That is:
+  :math:`a = 2 \arccos{W}`.
 
 Other considerations
 ====================