3×3 Determinants Using Diagonals

Initializing live version
Download to Desktop

Requires a Wolfram Notebook System

Interact on desktop, mobile and cloud with the free Wolfram Player or other Wolfram Language products.

Copy the first two columns of the matrix to its right. Multiply along the blue lines and the red lines. Add the numbers on the bottom and subtract the numbers on the top. The result is the value of the determinant.


This method does not work with 4×4 or higher-order determinants. For those, use expansion by minors or row reduction. Even when there are many zero entries, row reduction is more systematic, simpler, and less prone to error.


Contributed by: George Beck (March 2011)
Open content licensed under CC BY-NC-SA




Feedback (field required)
Email (field required) Name
Occupation Organization
Note: Your message & contact information may be shared with the author of any specific Demonstration for which you give feedback.