docs: angular quantities documentation improved

docs/framework/angular_units.rst

@@ -26,7 +26,7 @@ as early as 1936 and as recently as 2022. This would bring the advantages of a p
 unit system, with unambiguous units for all physical quantities. At the same time the only notable changes for typical
 end-users would be: improved units for the quantities **torque**, **angular momentum** and **moment of inertia**.
 
-Paul Quincey in his proposal `"Angles in the SI: a detailed proposal for solving the problem" <https://arxiv.org/pdf/2108.05704.pdf>`_ states:
+Paul Quincey in his proposal *"Angles in the SI: a detailed proposal for solving the problem"* [Quincey]_ states:
 
     The familiar units assigned to some angular quantities are based on equations that have adopted the radian convention,
     and so are missing `rad`s that would be present if the complete equation is used. The physically-correct units are
@@ -47,6 +47,17 @@ He proposes the following changes:
   **angular acceleration**, and **angular wavenumber** would be removed, the only correct SI units being
   :math:`rad`, :math:`rad/s`, :math:`rad/s`, :math:`rad/s^2` and :math:`rad/m` respectively.
 
+Paul Quincey summarizes that with the above in action:
+
+    However, the physical clarity this would build into the SI should be recognised very quickly. The units would tell us that
+    :math:`torque \times angle = energy`, and :math:`angular\:momentum \times angle = action`, for example, in the same way that they do for
+    :math:`force \times distance = energy`, :math:`linear\:momentum \times distance = action`, and
+    :math:`radiant\:intensity \times solid\:angle = radiant\:flux`.
+    Dimensional analysis could be used to its full extent. Software involving angular quantities would be rationalised.
+    Arguments about the correct units for frequency and angular frequency, and the meaning of the unit Hz, could be left behind.
+    The explanation of these changes would be considerably easier and more rewarding than explaining how a kilogram-sized mass
+    can be measured in terms of the Planck constant. 
+
 
 Angular quantities in the library
 ---------------------------------

docs/reference/systems/generic.rst

@@ -7,3 +7,4 @@ Generic
     generic/unknown
     generic/dimensionless
     generic/angle
+    generic/solid_angle

docs/reference/systems/generic/angle.rst

@@ -2,7 +2,12 @@ Angle
 =====
 
 .. doxygenstruct:: units::radian
+.. doxygenstruct:: units::rotation
+.. doxygenstruct:: units::degree
+.. doxygenstruct:: units::gradian
 
 .. doxygenstruct:: units::dim_angle
 
 .. doxygentypedef:: units::angle
+
+.. doxygenvariable:: cotes_angle

docs/reference/systems/generic/solid_angle.rst

@@ -0,0 +1,8 @@
+Solid Angle
+===========
+
+.. doxygenstruct:: units::steradian
+
+.. doxygenstruct:: units::dim_solid_angle
+
+.. doxygentypedef:: units::solid_angle

docs/references.rst

@@ -2,3 +2,4 @@ References
 ==========
 
 .. [ISO80000] `ISO 80000-1:2009(E) "Quantities and units — Part 1: General" <https://www.iso.org/standard/30669.html>`_, International Organization for Standardization.
+.. [Quincey] `"Angles in the SI: a detailed proposal for solving the problem" <https://arxiv.org/pdf/2108.05704.pdf>`_, Quincey, Paul (1 October 2021)