numpy.arccosh(x, /, out=None, *, where=True, casting='same_kind', order='K', dtype=None, subok=True[, signature, extobj]) = <ufunc 'arccosh'>
Inverse hyperbolic cosine, elementwise.
Parameters: 


Returns: 

arccosh
is a multivalued function: for each x
there are infinitely many numbers z
such that cosh(z) = x
. The convention is to return the z
whose imaginary part lies in [pi, pi]
and the real part in [0, inf]
.
For realvalued input data types, arccosh
always returns real output. For each value that cannot be expressed as a real number or infinity, it yields nan
and sets the invalid
floating point error flag.
For complexvalued input, arccosh
is a complex analytical function that has a branch cut [inf, 1]
and is continuous from above on it.
[1]  M. Abramowitz and I.A. Stegun, “Handbook of Mathematical Functions”, 10th printing, 1964, pp. 86. http://www.math.sfu.ca/~cbm/aands/ 
[2]  Wikipedia, “Inverse hyperbolic function”, https://en.wikipedia.org/wiki/Arccosh 
>>> np.arccosh([np.e, 10.0]) array([ 1.65745445, 2.99322285]) >>> np.arccosh(1) 0.0
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https://docs.scipy.org/doc/numpy1.17.0/reference/generated/numpy.arccosh.html