I will add to this page as I progress through matrices…

First off a **matrix** is a "rectangular array" of numbers. Or in other words a bunch of numbers that are arranged in rows and columns. For example:

The above matrix is of the **order** 3 x 3. Where the order is defined as the number of rows (3) by the number of columns (3). The following matrix is of order 3 x 2.

A **row** is defined as, well, a row… In the case above the numbers 1 and 3 are the first row and 7 and 9 are the third row. A **column** is likewise defined to be a column of numbers. In the case above 1 4 and 7 form the first column and 3 5 and 9 form the second column.

We often talk about an **element** of a matrix. In this case we are referring to a specific value. For example I might refer to the element in the second row and first column, which would be 4 in both examples above.

#### Notation

Matrices are often give an UPPER CASE letter as a symbol. For example:

(3)An element in the matrix *A* can be denoted by $a_{i,j}$, where the lower case *a* implies a connection to matrix *A* and the subscripts correlate to the row and column, respectively. For example $a_{3,3}=2$.

When scalar (regular) variables and matrix variables are shown together the matrix symbol(s) are often in bold for added clarity.

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