# arccosh function

(Shortest import: `from brian2 import arccosh)`

brian2.units.unitsafefunctions.arccosh(x, /, out=None, *, where=True, casting='same_kind', order='K', dtype=None, subok=True[, signature])

  Inverse hyperbolic cosine, element-wise.

  Parameters:

    x : array_like

    > Input array.

    out : ndarray, None, or tuple of ndarray and None, optional

    > A location into which the result is stored. If provided, it must have a shape that the inputs broadcast to. If not provided or None, a freshly-allocated array is returned. A tuple (possible only as a keyword argument) must have length equal to the number of outputs.

    where : array_like, optional

    > This condition is broadcast over the input. At locations where the condition is True, the `out` array will be set to the ufunc result. Elsewhere, the `out` array will retain its original value. Note that if an uninitialized `out` array is created via the default `out=None`, locations within it where the condition is False will remain uninitialized.

    **kwargs :

    > For other keyword-only arguments, see the ufunc docs.

  Returns:

    arccosh : ndarray

    > Array of the same shape as `x`. This is a scalar if `x` is a scalar.

  See also

  `cosh()`, `arcsinh()`, `sinh()`, `arctanh()`, `tanh()`

  Notes

  `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 real-valued 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 complex-valued input, `arccosh()` is a complex analytical function that has a branch cut `[-inf, 1]` and is continuous from above on it.

  References

  [R1]

  M. Abramowitz and I.A. Stegun, “Handbook of Mathematical Functions”, 10th printing, 1964, pp. 86. https://personal.math.ubc.ca/~cbm/aands/page_86.htm

  [R2]

  Wikipedia, “Inverse hyperbolic function”, https://en.wikipedia.org/wiki/Arccosh

  Examples

      >>> import numpy as np
      >>> np.arccosh([np.e, 10.0])
      array([ 1.65745445,  2.99322285])
      >>> np.arccosh(1)
      0.0