def get_aoi(self, surface_tilt, surface_azimuth, solar_zenith,<EOL>solar_azimuth):
aoi = irradiance.aoi(surface_tilt, surface_azimuth,<EOL>solar_zenith, solar_azimuth)<EOL>return aoi<EOL>
Get the angle of incidence on the system.

        For a given set of solar zenith and azimuth angles, the
        surface tilt and azimuth parameters are typically determined
        by :py:method:`~SingleAxisTracker.singleaxis`. The
        :py:method:`~SingleAxisTracker.singleaxis` method also returns
        the angle of incidence, so this method is only needed
        if using a different tracking algorithm.

        Parameters
        ----------
        surface_tilt : numeric
            Panel tilt from horizontal.
        surface_azimuth : numeric
            Panel azimuth from north
        solar_zenith : float or Series.
            Solar zenith angle.
        solar_azimuth : float or Series.
            Solar azimuth angle.

        Returns
        -------
        aoi : Series
            The angle of incidence in degrees from normal.