In mathematics, a vector is a quantity that cannot be represented only by a single unit. It has to be divided into 2 components, namely magnitude and direction. Geometrically, a vector can be represented by a line segment with an arrow attached at its end. the arrow points at the direction of the vector.

Vectors can be implemented in python in the form of arrays. The arrays can be assigned like normal arrays or as numpy arrays. Numpy arrays can be n-dimensional.

## Some properties of vectors

- When a vector is transmitted parallel to itself, it remains unchanged.
- Parallel vectors have the same direction.
- Vectors are said to be equal when they have the same magnitude and the direction.
- Vectors are said to be negative when they are equal in magnitude but opposite in direction.

In vector algebra we can calculate the angle between two vectors using a simple formula. The dot product of the two vectors can be used to determine the cosine of the angle between the two vectors which will ultimately give us our angle.

Let the two vectors be ‘* u*‘ and ‘

*‘ and the angle between them be ‘A’ . The formula is given below:*

**v**The numerator represents the dot product of the two vectors whereas the denominator is the multiplication of the magnitudes of the two vectors.

**Also read: Mocking in Python Using Unittest.mock**

## Using python to determine the angle between two vectors

We can use Python to compute the angle between two vectors using user-defined functions or by using functions from the numerical python( Numpy) library. The numpy library contains functions such as linalg.norm() and arccos() that makes calculations easier. to know more about numpy, click here.

### Implementing python functions for determining angles

We will be using the math library first and implement the function. The code for the program is as follows:

```
#importing required math module
import math
#calculating the magnitude of the vectors
def mag(u, N):
# Stores the final magnitude
magnitude = 0
# Traverse the array
for i in range(N):
magnitude += u[i] * u[i]
# Return the square root of magnitude
return math.sqrt(magnitude)
# Function to find the dot product of the vectors
def dotProd(u, v, N):
# Stores the dot product
prod = 0
# Traverse the array
for i in range(N):
prod = prod + u[i] * v[i]
# Return the product
return prod
def angleVector(u, v, N):
# Stores the dot product of vectors
dotProductOfVectors = dotProd(u, v, N)
# magnitude of vector u
magOfu = mag(u, N)
#magnitude of vector v
magOfv = mag(v, N)
# angle between given vectors
angle = (dotProductOfVectors
/ (magOfu * magOfv))
#display the angle
print('%.5f'%angle)
#pre defined vectors
u = [-0.5, -2, 1]
v = [-1, -1, 0.3]
# Size of the vectors
N = len(u)
#display the angle
print("The angle between the two vectors:")
#function call to calculate the angle between the vectors
angleVector(u, v, N)
```

The output of the above code will be the following:

```
The angle between the two vectors:
0.84529
```

### Using numpy to calculate the angle between two n-dimensional vectors

Now let’s look at how we can easily calculate the angle using numpy.

```
#importing the required modules
from numpy import arccos, array
from numpy.linalg import norm
import math
#function for calculating the angle using numpy
def angles(u, v):
#using the arccos function from numpy
return arccos(u.dot(v)/(norm(u)*norm(v)))
#defining the vectors
u = array([3, -4, 5])
v = array([2, 7, -3])
#function call to compute the angle
c= angles(u,v)
#the function returns the angle in radians
#converting the angle to degrees from radians
angle= math.degrees(c)
#displaying the result
print("the vectors are=",u,"and",v)
print("the angle between the two vectors is=",angle)
```

The output of the above code will look like something as follows:

```
the vectors are= [ 3 -4 5] and [ 2 7 -3]
the angle between the two vectors is= 131.647015792716
```

## Summary.

This tutorial explores the various ways in which one can calculate the angle between two n dimensional vectors in python. The two programs shown in this article, demonstrates the usage of the math and the numpy libraries for the same. Using the dot product of the two given vectors and by calculating their individual magnitudes, the cosine of the angle can be determined and is used to define the relationship between them.