from brian2 import arccos)
Trigonometric inverse cosine, element-wise.
The inverse of
cos()so that, if
y = cos(x), then
x = arccos(y).
x : array_like
x-coordinate on the unit circle. For real arguments, the domain is [-1, 1].
out : ndarray, optional
Array of the same shape as
a, to store results in. See
doc.ufuncs(Section “Output arguments”) for more details.
angle : ndarray
The angle of the ray intersecting the unit circle at the given
x-coordinate in radians [0, pi]. If
xis a scalar then a scalar is returned, otherwise an array of the same shape as
arccos()is a multivalued function: for each
xthere are infinitely many numbers
cos(z) = x. The convention is to return the angle
zwhose 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
nanand sets the
invalidfloating point error flag.
For complex-valued input,
arccos()is a complex analytic function that has branch cuts
[1, inf]and is continuous from above on the former and from below on the latter.
cos()is also known as
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()