# Matrix Operations

**Task: **Enter matrices A, B, and C into your calculator

** Method :**

1) Hit the MATRX key and use the arrows to highlight EDIT. Since matrix [A] is
already

highlighted, you can just press ENTER .

2) You are now ready to enter matrix A into your calculator. First you need
to tell the calculator

the size of matrix A. Press 3 for the row size, then ENTER. Press 3 for the
column size then

ENTER. The calculator now displays a 3 by 3 matrix.

3) Type each entry in the matrix going across rows. Press ENTER after each
entry. If there are

already numbers in the matrix , you can just type the new numbers over the old.

4) Verify that you typed each entry correctly. If a mistake was made, use
your arrow keys to go

to the correct location and change the entry . Press 2^{nd} QUIT to exit the Matrix
editor.

5) Enter matrices B and C into your calculator. You will need to begin with
Step 1 each time ,

selecting [B] and [C].

**Task: Add or Subtract matrices :**

** Method :**

1) Make sure you are on the Home screen of your calculator. Press 2^{nd}
QUIT if you are not

sure.

2) Press MATRX and note that NAMES and 1: are highlighted. Press ENTER to
select Matrix A

and return to the Home screen.

3) Press +.

4) Press MATRX. Use the down arrow to highlight Matrix B. Once it is
highlighted, press

ENTER to select Matrix B and return to your home screen.

5) Press ENTER and the calculator will perform the addition.

6) Try adding matrix B to matrix C. You should get a dimension mismatch
error. Matrices must

be the same size in order to add or subtract them.

**Task: **Multiply a matrix by a scalar:

**Method:**

1) On your home screen type -7 *.

2) Press MATRX. Use the down arrow to highlight matrix C. Once it is
highlighted, press

ENTER to select matrix C and return to your home screen.

3) Press ENTER and the calculator will perform the multiplication.

**Task: Multiply two matrices :**

**Method:**

1) Be sure you are on the Home screen. Press MATRX. Use the down arrow to
highlight matrix

B. Once it is highlighted, press ENTER to select matrix B and return to your
home screen.

2) Press *

3) Press MATRX. Use the down arrow to highlight matrix C. Once it is
highlighted, press

ENTER to select matrix C and return to your home screen.

4) Press ENTER and the calculator will perform the multiplication.

5) Try multiplying matrix C * matrix B. You should get a dimension mismatch
error. The

number of columns of the first matrix, must match the number of rows of the
second matrix.

**Task: Determine the inverse of a matrix:**

**Method:**

1) Be sure you are on the Home screen. Press MATRX. Verify that matrix A is
highlighted. Once

it is highlighted, press ENTER to select matrix A and return to your home
screen.

2) Press the inverse key on your calculator: x^{-1}

3) Press ENTER to have the calculator determine the inverse.

4) You may want to change the results to fractions by pressing MATH;
highlighting Frac and

then pressing ENTER.

5) If you try to determine the inverse of matrix C, you will get an invalid
dimension error. Only

square matrices have inverses.

**Task: Determine the determinant of a matrix
Method:**

1) The determinant function is part of the matrix math menu . Press 2^{nd} MATRX
and use the

right arrow to go over to the MATH menu. The first command is for determinant.

2) To calculate the determinant of Matrix A, press ENTER
to select item 1. You will now

be brought back to the home screen. Now select Matrix A by pressing 2^{nd}
MATRX and

from the NAMES menu selecting [A]. Again you will be returned to the home
screen.

3) Close the parentheses and press ENTER to get the value of the determinant .

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