calc_zeta_inf
=============

.. py:function:: luminet.black_hole_math.calc_zeta_inf(p: float, bh_mass: float) -> float

   Calculate :math:`\zeta_\infty`

   This is used in the Jacobi incomplete elliptic integral :math:`F(\zeta_\infty, k)`

   .. math::

      \zeta_\infty = \arcsin \left( \sqrt{\frac{Q - P + 2M}{Q - P + 6M}} \right)

   :Parameters: * **p** (*float*) -- periastron distance
                * **bh_mass** (*float*) -- Black hole mass

   :returns: *float* -- :math:`\zeta_\infty`