HP 39g Graphing Calculator - Manual (Page 181)

To multiply two
matrices
To divide by a
square matrix
To multiply the two matrices Ml and M2 that you created for
the previous example, use the following keystrokes:
[ alpha |M1 g |7I pha 1M2
ENTER
RnsA2
Ml «-MS
CCS,4],[5,633
[[19,223,[43,5033
BEBB
To multiply a matrix by a vector, enter the matrix first, then
the vector. The number of elements in the vector must equal
the number of columns in the matrix.
For division of a matrix or a vector by a square matrix, the
number of rows of the dividend (or the number of elements, if
it is a vector) must equal the number of rows in the divisor.
This operation is not a mathematical division: it is a left-
multiplication by the inverse of the divisor. M1/M2 is
equivalent to M2'"’ * Ml.
To divide the two matrices M1 and M2 that you created for the
previous example, use the following keystrokes:
[ alpha IMI g [ alpha |M2
ENTER
[[19,223,[43,5033
M
1
/-M
2
[C5,43,[-4,-333
To invert a matrix
To negate each
element
You can invert a square matrix in HOME by typing the matrix
(or its variable name) and pressing
[ shift [ enter ] . Or you
can use the matrix INVERSE command. Enter
IHVERSEimathxname) in HOME and press [ ent | r ].
You can change the sign of each element in a matrix by
pressing [TT| before the matrix name.
Matrices 12-7