numpy.arccos#

numpy.arccos(x,/,out=None,*,where=True,casting='same_kind',order='K',dtype=None,subok=True[,signature])=<ufunc'arccos'>#

Trigonometric inverse cosine, element-wise.

The inverse ofcos so that, ify=cos(x), thenx=arccos(y).

Parameters:

xarray_like

x-coordinate on the unit circle.For real arguments, the domain is [-1, 1].

outndarray, None, or tuple of ndarray and None, optional

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

wherearray_like, optional

This condition is broadcast over the input. At locations where thecondition is True, theout array will be set to the ufunc result.Elsewhere, theout array will retain its original value.Note that if an uninitializedout array is created via the defaultout=None, locations within it where the condition is False willremain uninitialized.

**kwargs

For other keyword-only arguments, see theufunc docs.

Returns:

anglendarray

The angle of the ray intersecting the unit circle at the givenx-coordinate in radians [0, pi].This is a scalar ifx is a scalar.

See also

cos,arctan,arcsin,emath.arccos

Notes

arccos is a multivalued function: for eachx there are infinitelymany numbersz such thatcos(z)=x. The convention is to returnthe anglez whose real part lies in[0, pi].

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 yieldsnan and sets theinvalid floating point error flag.

For complex-valued input,arccos is a complex analytic function thathas branch cuts[-inf,-1] and[1, inf] and is continuous fromabove on the former and from below on the latter.

The inversecos is also known asacos or cos^-1.

References

M. Abramowitz and I.A. Stegun, “Handbook of Mathematical Functions”,10th printing, 1964, pp. 79.https://personal.math.ubc.ca/~cbm/aands/page_79.htm

Examples

Try it in your browser!

>>>importnumpyasnp

We expect the arccos of 1 to be 0, and of -1 to be pi:

>>>np.arccos([1,-1])array([ 0.        ,  3.14159265])

Plot arccos:

>>>importmatplotlib.pyplotasplt>>>x=np.linspace(-1,1,num=100)>>>plt.plot(x,np.arccos(x))>>>plt.axis('tight')>>>plt.show()

Go BackOpen In Tab