## Permutation matrices

### Definition and example

Let denote the th unit row-vector (the th component is 1 and the others are zeros).

**Definition 1**. A **permutation matrix** is defined by two conditions: a) all of its rows are unit row-vectors and b) no two rows are equal. We use the notation

where all rows are different.

**Example**. In the following matrix we change places of rows in such a way as to obtain the identity in the end. Each transformation changes the sign of the matrix by Property VI.

Since there are three changes and the final matrix is identity, by Axiom 3 .

It is possible to arrive to the identity matrix in more than one way but the result will be the same because the number is fixed. Calculating determinants of permutation matrices in this way allows us to avoid studying the theory of permutations.

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