# mars.tensor.arctan¶

mars.tensor.arctan(x, out=None, where=None, **kwargs)[source]

Trigonometric inverse tangent, element-wise.

The inverse of tan, so that if y = tan(x) then x = arctan(y).

x : array_like out : Tensor, None, or tuple of Tensor 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 tensor is returned. A tuple (possible only as a keyword argument) must have length equal to the number of outputs.
where : array_like, optional
Values of True indicate to calculate the ufunc at that position, values of False indicate to leave the value in the output alone.

**kwargs

out : Tensor
Out has the same shape as x. Its real part is in [-pi/2, pi/2] (arctan(+/-inf) returns +/-pi/2). It is a scalar if x is a scalar.
arctan2 : The “four quadrant” arctan of the angle formed by (x, y)
and the positive x-axis.

angle : Argument of complex values.

arctan is a multi-valued function: for each x there are infinitely many numbers z such that tan(z) = x. The convention is to return the angle z whose real part lies in [-pi/2, pi/2].

For real-valued input data types, arctan 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, arctan is a complex analytic function that has [1j, infj] and [-1j, -infj] as branch cuts, and is continuous from the left on the former and from the right on the latter.

The inverse tangent is also known as atan or tan^{-1}.

Abramowitz, M. and Stegun, I. A., Handbook of Mathematical Functions, 10th printing, New York: Dover, 1964, pp. 79. http://www.math.sfu.ca/~cbm/aands/

We expect the arctan of 0 to be 0, and of 1 to be pi/4: >>> import mars.tensor as mt

>>> mt.arctan([0, 1]).execute()
array([ 0.        ,  0.78539816])

>>> mt.pi/4
0.78539816339744828


Plot arctan:

>>> import matplotlib.pyplot as plt
>>> x = mt.linspace(-10, 10)
>>> plt.plot(x.execute(), mt.arctan(x).execute())
>>> plt.axis('tight')
>>> plt.show()