# Python – math.acos() function

Math module contains a number of functions which is used for mathematical operations. The math.acos() function returns the arc cosine value of a number. The value passed in this function should be in between -1 to 1.

Syntax: math.acos(x)

Parameter:This method accepts only single parameters.

• x :This parameter is the value to be passed to acos()

Returns:This function returns the arc cosine value of a number.

Below examples illustrate the use of above function:

Example 1:

 `# Python code to implement ` `# the acos()function ` `      `  `# importing "math" ` `# for mathematical operations   ` `import` `math   ` `     `  `a ``=` `math.pi ``/` `6` `      `  `# returning the value of arc cosine of pi / 6   ` `print` `(``"The value of arc cosine of pi / 6 is : "``, end ``=``"")   ` `print` `(math.acos(a)) `

Output:

```The value of arc cosine of pi / 6 is : 1.0197267436954502
```

Example 2:

 `# Python code implementation of  ` `# the acos() function ` `import` `math  ` `import` `numpy as np  ` `import` `matplotlib.pyplot as plt   ` `   `  `in_array ``=` `np.linspace(``-``(``1` `/` `3.5` `*` `np.pi), ``1` `/` `3.5` `*` `np.pi, ``20``)  ` `   `  `out_array ``=` `[]  ` `   `  `for` `i ``in` `range``(``len``(in_array)):  ` `    ``out_array.append(math.acos(in_array[i]))  ` `    ``i ``+``=` `1` `    `  `print``(``"Input_Array : \n"``, in_array)   ` `print``(``"\nOutput_Array : \n"``, out_array)   ` ` `  ` `  `plt.plot(in_array, out_array, ``"go-"``)   ` `plt.title(``"math.acos()"``)   ` `plt.xlabel(``"X"``)   ` `plt.ylabel(``"Y"``)   ` `plt.show()  `

Output:

```Input_Array :
[-0.8975979  -0.80311391 -0.70862992 -0.61414593 -0.51966194 -0.42517795
-0.33069396 -0.23620997 -0.14172598 -0.04724199  0.04724199  0.14172598
0.23620997  0.33069396  0.42517795  0.51966194  0.61414593  0.70862992
0.80311391  0.8975979 ]

Output_Array :
[2.6850860217724004, 2.50329950258761, 2.358350863035667, 2.2320996324218134,
2.1172515505585388, 2.009954812757658, 1.9078351422171613, 1.809259917693194,
1.7130011090538158, 1.6180559117526183, 1.5235367418371748, 1.4285915445359774,
1.3323327358965993, 1.233757511372632, 1.131637840832135, 1.0243411030312544,
0.9094930211679799, 0.783241790554126, 0.6382931510021833, 0.45650663181739287]
```

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