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- Posts: **32,260** 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

336MemberThe 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)

52Junior 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.

32,260Senior MemberHowever, is there any way to compute 4X4 matrices with variables instead of numbers??

2,142Senior Member32,260Senior Member336Member32,260Senior Member1New 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