numpy.arccos(x, /, out=None, *, where=True, casting='same_kind', order='K', dtype=None, subok=True[, signature, extobj]) = <ufunc 'arccos'>
Trigonometric inverse cosine, element-wise.
The inverse of
cos so that, if
y = cos(x), then
x = arccos(y).
arccos is a multivalued function: for each
x there are infinitely many numbers
z such that
cos(z) = x. The convention is to return the angle
z whose real part lies in
For real-valued input data types,
arccos 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,
arccos is a complex analytic function that has branch cuts
[-inf, -1] and
[1, inf] and is continuous from above on the former and from below on the latter.
cos is also known as
acos or cos^-1.
M. Abramowitz and I.A. Stegun, “Handbook of Mathematical Functions”, 10th printing, 1964, pp. 79. http://www.math.sfu.ca/~cbm/aands/
We expect the arccos of 1 to be 0, and of -1 to be pi:
>>> np.arccos([1, -1]) array([ 0. , 3.14159265])
>>> import matplotlib.pyplot as plt >>> x = np.linspace(-1, 1, num=100) >>> plt.plot(x, np.arccos(x)) >>> plt.axis('tight') >>> plt.show()
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