From A First Course in Linear Algebra
Version 2.21
© 2004.
Licensed under the GNU Free Documentation License.
http://linear.ups.edu/
On the TI86, press the MATRX key (Yellow7) . Press the second menu key over, F2 , to bring up the EDIT screen. Give your matrix a name, one letter or many, then press ENTER . You can then change the size of the matrix (rows, then columns) and begin editing individual entries (which are initially zero). ENTER will move you from entry to entry, or the down arrow key will move you to the next row. A menu gives you extra options for editing.
Matrices may also be entered on the home screen as follows. Use brackets ([ , ]) to enclose rows with elements separated by commas. Group rows, in order, into a final set of brackets (with no commas between rows). This can then be stored in a name with the STO key. So, for example,
[[1, 2, 3, 4]\ [5, 6, 7, 8]\ [9, 10, 11, 12]] → A

will create a matrix named A that is equal to
\left [\array{
1& 2 & 3 & 4\cr
5& 6 & 7 & 8
\cr
9&10&11&12 } \right ]

If A is the name of a matrix stored in the TI86, then the command rref A will return the reduced rowechelon form of the matrix. This command can also be found by pressing the MATRX key, then F4 for OPS , and finally, F5 for rref .
Note that this command will not work for a matrix with more rows than columns. (Ed. Not sure just why this is!) A workaround is to pad the matrix with extra columns of zeros until the matrix is square.
Contributed by Robert Beezer
Vector operations on the TI86 can be accessed via the VECTR key, which is
Yellow8 . The EDIT tool appears when the F2 key is pressed. After providing
a name and giving a “dimension” (the size) then you can enter the individual
entries, one at a time. Vectors can also be entered on the home screen using
brackets ( [ , ] ). To create the vector
v = \left [\array{
1\cr
2
\cr
3\cr
4 } \right ]

use brackets and the store key ( STO ),
[1,\kern 1.95872pt 2,\kern 1.95872pt 3,\kern 1.95872pt 4] → v

Vector addition and scalar multiplication are then very natural. If u and v are two vectors of equal size, then
2 ∗ u + (−3) ∗ v

will compute the correct vector and display the result as a vector.
Contributed by Eric Fickenscher
Suppose A is the name of a matrix stored in the TI86. Use the command
{A}^{T } to transpose
A . This command can be found by pressing the MATRX key, then F3 for MATH , then F2
for {}^{T }.