# How to Calculate Inverse of Cosine in Python

Jay Prakash Gupta Feb 02, 2024

The inverse of cosine is the trigonometric function which is widely used to solve many problems in trignometry. The inverse of cosine is also called arc cosine. We can calculate the inverse of cosine in Python using the `math.acos()` function and NumPy library.

## Calculate Inverse of Cosine Using `math.acos()` Function in Python

``````import math

print(math.acos(0.2))
print(math.acos(0.8))
print(math.acos(0))
print(math.acos(1))
``````

Output:

``````1.369438406004566
0.6435011087932843
1.5707963267948966
0.0
``````

First of all, we need to import the math library and then apply the `math.acos()` function to our input value to find the inverse of cosine.Inverse of cosine using the `acos()` function gives the result in radians.

## Calculate Inverse of Cosine Using `degrees()` and `acos()` Function in Python

Inverse of cosine using the `acos()` function gives the result in radians. If we need to find the inverse of cosine output in degrees instead of radian then we can use the `degrees()` function with the `acos()` function.

``````import math

print(result)
print(math.degrees(result))  # degree
``````

Output:

``````1.369438406004566
78.46304096718453
``````

Here, we first get the inverse of cosine in radian and store it in the `result` variable. Then we apply the `degrees()` function to the result variable to get the final value in degrees.

We can see that we get the output as a floating-point number. We can fix it to any number of decimal places.

``````import math

result = math.acos(0.2)
print("%.2f" % result)
``````

Output:

``````1.37
``````

In this way, we can use the formatting of float values in Python to the inverse of cosine.

## Calculate Inverse of Cosine Using Python NumPy Library

We can find the inverse of cosine using the NumPy library. The advantage of using the NumPy library is that we can find the inverse of cosine of range of elements all at once.

``````import numpy as np

print(np.arccos(0.2))
print(np.arccos([0.2, 0.8, 0, 0.5]))
``````

Output:

``````1.369438406004566
[1.36943841 0.64350111 1.57079633 1.04719755]
``````

Here, the NumPy library provides us with an `arccos()` function to find the inverse of cosine. Either we can give a single value to the `arccos()` function or a list of values.