Assy docs fix (#614)

Author: adam-urbanczyk

doc/primer.rst

@@ -262,8 +262,8 @@ using tags. Tags can be directly referenced when constructing the constraints::
 
 The following constraints are currently implemented:
 
-   :Axis: two normal vectors are anti-coincident or the cosine of the angle between them is equal to the specified value. Can be defined for all entities with consistent normal vector - planar faces, wires and edges.
+   :Axis: two normal vectors are anti-coincident or the angle (in radians) between them is equal to the specified value. Can be defined for all entities with consistent normal vector - planar faces, wires and edges.
    :Point: two points are coincident or separated by a specified distance. Can be defined for all entities, center of mass is used for lines, faces, solids and the vertex position for vertices.
    :Plane: combination of :Axis: and :Point: constraints.
 
-For a more elaborate assembly example see :ref:`assytutorial`.
+For a more elaborate assembly example see :ref:`assytutorial`.