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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def fraction_illuminated(ephemeris, body, t):
 """Compute the illuminated fraction of a body viewed from Earth. The ``body`` should be an integer or string that can be looked up in the given ``ephemeris``, which will also be asked to provide positions for the Earth and Sun. The return value will be a floating point number between zero and one. This simple routine assumes that the body is a perfectly uniform sphere. """

    a = phase_angle(ephemeris, body, t).radians
    return 0.5 * (1.0 + cos(a))