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Determinants: (lesson 1 of 2)

Introduction to Determinant

In the following we assume we have a square matrix (m=n)(m=n). The determinant of a matrix AA will be denoted by det(A)\det(A) or A|A|.

Determinant of a 2 ×\times 2 matrix

Assuming AA is an arbitrary 2 ×\times 2 matrix AA, where the elements are given by: A = \left( {} \right)

then the determinant of this matrix is as follows:

\det (A) = \left| A \right| = \left| {} \right| = {a_{11}}{a_{22}} - {a_{21}}{a_{12}}

Determinant of a 3 ×\times 3 matrix

The determinant of a 3 ×\times 3 matrix is a little more tricky and is found as follows ( for this case assume AA is an arbitrary 3 ×\times 3 matrix AA, where the elements are given below)

A = \left( {} \right)

then the determinant of this matrix is as follows:

\det (A) = \left| {} \right| = {a_{11}}\left| {} \right| - {a_{12}}\left| {} \right| + {a_{13}}\left| {} \right|