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This movie will introduce use of the matrix tool and use it to do some very simple matrix
operations using addition and subtraction only. Let's create a matrix A and we'll give
it 2 rows and 3 columns. In the first row I'll put some numbers, and in the second row.
So that finishes defining A now let's define B the same size as A 2 rows and 3 columns.
So I've now defined A and B. Each with 2 rows and 3 columns. To see that it understands
them let's have the program print out each one of them for us. That's what A looks like.
That's what B looks like. Now let's have the matrix tool add them for us. Click the compute
button and it gives the sum of A and B. I could do it in the opposite order and get
the same thing of course. I can subtract the matrices A minus B and it gives me that. Let's
check one! of the entries. Let's check the entry in row 1 column 3. 7 minus 25 would
be the minus 18 shown here. And finally let's do an example to illustrate work with fractions.
So I'm going to click the button that says erase everything. Now let's create 2 new matrices
with fractions. Let's say A is 2 by 2 matrix one half one third in the first row and five
sixths one fourth in the second row. And let's let matrix B be two and one third in the first
row and minus 3 and four thirds in the second row. And let's see what it does if we come
down and put the program into fraction mode. So we're going to ask it to give us our entries as
fractions by selecting that check box that says fraction mode. Now let's see what A plus
B looks like. We compute A plus B and this is what we get. Is that right? For the first
row first column we have one half plus 2 would be two and a half which it is written in fraction
form ! as five halves?..one-third plus one-third is two thirds for! the first row second column
entry. And if you five sixths then minus 3 you'll get minus two and a sixth which can
be written this way in fraction mode if you write it as a fraction reduced to lowest terms.
So if you check this you'll find that this is correct. So you have the option of working
in either decimal mode or fraction mode and we've just illustrated the use of the matrix
tool to add and subtract matrices.