Converts spherical polar coordinates to rectangular cartesian coordinates.
Note that the input angles should be in latitude/longitude or elevation/azimuthal form. I.e., the origin is along the equator rather than at the north pole.
Note
This is a low-level function used internally in astropy.coordinates. It is provided for users if they really want to use it, but it is recommended that you use the astropy.coordinates coordinate systems.
| Parameters: | r : scalar or array-like 
 lat : scalar or array-like 
 lon : scalar or array-like 
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|---|---|
| Returns: | x : float or array 
 y : float or array 
 z : float or array 
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