Determinant of a 3x3 matrix

Last updated: Jan. 2nd, 2019
Find the determinant of a 3x3 matrix,
, by using the cofactor expansion.

Explanation

The cofactor expansion of $A$ along the first column is

Calculating the 2x2 determinant in each term,
From these, we obtain
Example:
The determinant of
is
Calculator
Enter a 3x3 matrix and press "Execute" button. Then the determinant is displayed.
 1 2 3 1 2 3
$|A|$ =