Idempotent matrix

An idempotent matrix is a special kind of matrix which, when multiplied by itself, will always give you the same result. For example, if you have a matrix that looks like this:

[2 3]
[1 4]

And you multiply it by itself, like this:
[2 3] x [2 3]
[1 4] [1 4]

You will always get the same result:
[4 6]
[2 8]

Idempotent matrices can be helpful in mathematical calculations because it can save time if you know you will always get the same result.