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Posts: **32,210**- 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.

32,210- Senior MemberHowever, is there any way to compute 4X4 matrices with variables instead of numbers??

2,142Registered User Senior Member32,210- Senior Member336Registered User Member32,210- 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