Python cos – Find Cosine of Number in Radians Using math.cos()

To find the cosine of a number (in radians), we can use the Python cos() function from the math module.

import math

math.cos(x)

In Python, we can easily use trigonometric functions with the Python math module. The Python math module allows us to perform trigonometry easily.

With the Python math module, we can find the cosine of a number easily.

To find the cosine of a number, in radians, we use the math cos() function.

Below is the Python syntax to find the cosine of a number.

import math

math.cos(x)

The input to the cos() function must be a numeric value. The return value will be a numeric value between -1 and 1.

import math

print(math.cos(math.pi/3))
print(math.cos(0))
print(math.cos(math.pi/2))

#Output: 
0.5000000000000001
1.0
6.123233995736766e-17

Converting Degrees to Radians for Input into cos()

The cos() function takes a number in radians as input. If your data is in degrees, you will need to convert the values to radians.

The Python math module has a useful function to convert degrees to radians, the math radians() function.

If we have a value in degrees, we can use radians() to convert the value to radians and then pass it to the cos() function.

import math

print(math.cos(math.radians(60)))
print(math.cos(0))
print(math.cos(math.radians(90)))

#Output: 
0.5000000000000001
1.0
6.123233995736766e-17

Finding the Inverse Cosine of a Number in Python

The Python math module also provides us trigonometric functions to find the inverses of the common trigonometric functions. The acos() function allows us to find the inverse of the cosine of a number.

Below, we show that if we pass a number to cos() and then call the Python acos() function, we get back the same number.

import math

print(math.acos(math.cos(math.pi/3)))
print(math.pi/3)

#Output: 
1.0471975511965976
1.0471975511965976

Finding the Secant of a Number in Python

To find the secant of a number, we can divide 1 by the cosine of the number.

We can find the secant of a number easily with the Python cos() function. You can see how to find the secant of a number in the following Python code.

import math

print(1/math.cos(math.pi/3))

#Output: 
1.9999999999999996

Hopefully this article has been beneficial for you to understand how to use the math cos() function in Python to find the cosine of a number.