# megengine.functional.acos¶

acos(x)[源代码]

Element-wise $$\arccos(x)$$ function.

Calculates an approximation to the inverse cosine for each element $$x_i$$ of the input tensor $$x$$. Each element-wise result is expressed in radians.

This function has domain [-1, +1] and codomain [0, pi].

The inverse of $$\cos$$ so that, if $$y = \cos(x)$$, then $$x = \arccos(y)$$.

x – input tensor. Should have a floating-point data type.

a tensor containing the inverse cosine of each element in $$x$$. The returned tensor must have a floating-point data type determined by 类型提升规则.

Special cases

For floating-point operands,

• If $$x_i$$ is NaN, the result is NaN.

• If $$x_i$$ is greater than 1, the result is NaN.

• If $$x_i$$ is less than -1, the result is NaN.

• If $$x_i$$ is 1, the result is +0.

>>> F.acos(1)
Tensor(0.0, device=xpux:0)


Element-wise inverse cosine:

>>> import math
>>> x = Tensor([0, 1, -1])
>>> F.acos(x)
Tensor([1.5708 0.     3.1416], device=xpux:0)