# Python | Tensorflow acos() method

• Last Updated : 07 Jan, 2022

Tensorflow is an open-source machine learning library developed by Google. One of its applications is to develop deep neural networks.

The module `tensorflow.math` provides support for many basic mathematical operations. Function `tf.acos()` [alias `tf.math.acos`] provides support for the inverse cosine function in Tensorflow. It expects the input to be in the range [-1, 1] and gives the output in radian form. It returns nan if the input does not lie in the range [-1, 1]. The input type is tensor and if the input contains more than one element, element-wise inverse cosine is computed.

Syntax: tf.acos(x, name=None) or tf.math.acos(x, name=None)

Parameters:
x: A tensor of any of the following types: bfloat16, half, float32, float64, int32, int64, complex64, or complex128.
name (optional): The name for the operation.

Return type: A tensor with the same type as that of x.

Code #1:

## Python3

 `# Importing the Tensorflow library``import` `tensorflow as tf`` ` `# A constant vector of size 6``a ``=` `tf.constant([``1.0``, ``-``0.5``, ``3.4``, ``0.2``, ``0.0``, ``-``2``],``                            ``dtype ``=` `tf.float32)`` ` `# Applying the acos function and``# storing the result in 'b'``b ``=` `tf.acos(a, name ``=``'acos'``)`` ` `# Initiating a Tensorflow session``with tf.Session() as sess:``    ``print``(``'Input type:'``, a)``    ``print``(``'Input:'``, sess.run(a))``    ``print``(``'Return type:'``, b)``    ``print``(``'Output:'``, sess.run(b))`

Output:

```Input type: Tensor("Const_7:0", shape=(6, ), dtype=float32)
Input: [ 1.  -0.5  3.4  0.2  0.  -2. ]
Return type: Tensor("acos:0", shape=(6, ), dtype=float32)
Output: [0.        2.0943952       nan 1.3694384 1.5707964       nan]
```

Code #2: Visualization

## Python3

 `# Importing the Tensorflow library``import` `tensorflow as tf`` ` `# Importing the NumPy library``import` `numpy as np`` ` `# Importing the matplotlib.pyplot function``import` `matplotlib.pyplot as plt`` ` `# A vector of size 15 with values from -1 to 1``a ``=` `np.linspace(``-``1``, ``1``, ``15``)`` ` `# Applying the inverse cosine function and``# storing the result in 'b'``b ``=` `tf.acos(a, name ``=``'acos'``)`` ` `# Initiating a Tensorflow session``with tf.Session() as sess:``    ``print``(``'Input:'``, a)``    ``print``(``'Output:'``, sess.run(b))``    ``plt.plot(a, sess.run(b), color ``=` `'red'``, marker ``=` `"o"``) ``    ``plt.title(``"tensorflow.acos"``) ``    ``plt.xlabel(``"X"``) ``    ``plt.ylabel(``"Y"``) `` ` `    ``plt.show()`

Output:

```Input: [-1.         -0.85714286 -0.71428571 -0.57142857 -0.42857143 -0.28571429
-0.14285714  0.          0.14285714  0.28571429  0.42857143  0.57142857
0.71428571  0.85714286  1.        ]
Output: [3.14159265 2.60049313 2.36639928 2.17904191 2.01370737 1.86054803
1.7141439  1.57079633 1.42744876 1.28104463 1.12788528 0.96255075
0.77519337 0.54109953 0.        ]
```

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