Sign Up For Free

**Join for FREE**,
and start talking with other members, weighing in on community polls,
and more.

Also, by registering and logging in you'll see fewer ads and pesky welcome messages (like this one!)

- Reply to threads, and start your own
- Create reports of your
**campus visits** - Share college
**photos**and**videos** **Find your dream college**, save your search and share with friends- Receive our
**monthly newsletter**

College Confidential’s “Dean,” Sally Rubenstone, put together 25 of her best tips. Get your free copy of the "25 Tips from the Dean" eBook and get helpful advice on how to choose a college, get in, and pay for it: http://goo.gl/9zDJTM

CC Articles
Posts: **2,695**- Senior Member

How do I use the TI-89 to find the determinants of 3X3 and 4X4 matrices? I only know how to do 2X2, but that would be a waste of time since I can cross multiply.

Any idea ??

Any idea ??

Post edited by Unknown User on

## Replies to: Matrices on the TI-89

336Registered User MemberThe format is

(the bracket key is located on the comma key (2nd comma) which is immediately left of division):

[[1,2,3][4,5,6][7,8,9]]

This produces a 3x3 like this:

|1 2 3|

|4 5 6|

|7 8 9|

Then you can use the standard matrix operator functions under 2nd Math to find the determinant. For the previous matrix, the determinant would be typed in as follows:

2nd -> Math -> det( -> <matrix> -> )

OR

det([[1,2,3][4,5,6][7,8,9]])

52Registered User Junior Member2nd-->Math-->Matrix-->newMat(

and then type in the dimensions: newMat(rows, columns)

You get a matrix of all 0's, which you can then replace rather quickly with anything at all.

2,695- Senior MemberHowever, is there any way to compute 4X4 matrices with variables instead of numbers??

2,142Registered User Senior Member2,695- Senior Member336Registered User Member2,695- Senior Member1Registered User New MemberIf you get "error: non algebraic variable in expression" that means you have something stored in one of your variables. To fix this, press 2nd, f1, 1, enter.

Cheers