def solar_zenith_analytical(latitude, hourangle, declination):
return np.arccos(<EOL>np.cos(declination) * np.cos(latitude) * np.cos(hourangle) +<EOL>np.sin(declination) * np.sin(latitude)<EOL>)<EOL>
Analytical expression of solar zenith angle based on spherical
trigonometry.

.. warning:: The analytic form neglects the effect of atmospheric
    refraction.

Parameters
----------
latitude : numeric
    Latitude of location in radians.
hourangle : numeric
    Hour angle in the local solar time in radians.
declination : numeric
    Declination of the sun in radians.

Returns
-------
zenith : numeric
    Solar zenith angle in radians.

References
----------
[1] J. A. Duffie and W. A. Beckman,  "Solar Engineering of Thermal
Processes, 3rd Edition" pp. 14, J. Wiley and Sons, New York (2006)

[2] J. H. Seinfeld and S. N. Pandis, "Atmospheric Chemistry and
Physics" p. 132, J. Wiley (1998)

[3] Daryl R. Myers, "Solar Radiation: Practical Modeling for
Renewable Energy Applications", p. 5 CRC Press (2013)

`Wikipedia: Solar Zenith Angle
<https://en.wikipedia.org/wiki/Solar_zenith_angle>`_

`PVCDROM: Sun's Position
<http://www.pveducation.org/pvcdrom/2-properties-sunlight/suns-position>`_

See Also
--------
declination_spencer71
declination_cooper69
hour_angle