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« Basic Operations with Vectors |

Linear Algebra - Vectors: (lesson 2 of 3)

Definition:

The dot product (also called the inner product or scalar product) of two vectors is defined as:

Where |A| and |B| represents the magnitudes of vectors A and B and is the angle between vectors A and B.

The dot or scalar product of vectors and can be written as:

Example (calculation in two dimensions):

Vectors **A** and **B** are given by and
. Find the dot product
of the two vectors.

Solution:

Example (calculation in three dimensions):

Vectors **A** and **B** are given by and
. Find the dot product
of the two vectors.

Solution:

The length of a vector is:

Example:

Vector **A** is given by .
Find **|A|**.

Solution:

The angle between two nonzero vectors **A** and **B** is

Example: (angle between vectors in two dimensions):

Determine the angle between and .

Solution:

We will need the magnitudes of each vector as well as the dot product.

The angle is,

Example: (angle between vectors in three dimensions):

Determine the angle between and .

Solution:

Again, we need the magnitudes as well as the dot product.

The angle is,

If two vectors are **orthogonal** then:
.

Example:

Determine if the following vectors are **orthogonal**:

Solution:

The dot product is

So, the two vectors are orthogonal.