Matrix: Putting it Together: Addition, Subtraction, Scalar Multiplication and Transpose

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We can use the GNRNDM program with the key values 63100700900, 2424424242 and 0 to generate the matrices:

The calculator used to obtain the images below was a TI 84 Plus running the 2.55MP operating system and it was in the MATHPRINT display mode. These images merely reflect generating the matrices.


In previous web pages we have looked at,among other things, matrix addition, scalar multiplication, subtraction, and transpose. All of these topics work together. Here we will look at evaluating the more complex expressions In each case we will just construct the appropriate command on our TI-83/84 calculator and have the machine find the answer. You should, in each case, verify that the answer is just what you would obtain if you did the problem by hand.
Figure 01
5[A]+3[B]
Figure 02
Both ([A]+[B])T and [A]T+[B]T. Notice that the results are identical. The general rule is that the transpose of a sum of matrices is the the same as the sum of the transposes of the matrices.
Figure 03
Although [A] and [D] do not have the same dimensions, [A] and [D]T are both 4 x 3 matrices and therefore we can add them. Note that this works because transpose has a higher precedence than does addition. Therefore we need to find the transpose of [D] before we add the two values.
Figure 04
Here is a slightly more complex version of the same issue. We know that transpose has a higher precedence than addition, and therefore a higher precedence than subtraction. There is a question about the relation of transpose to scalar multiplication. This example does not resolve that question. However, since scalar multiplication can be thought of as a replacement for repeated addition, and because the "transpose of a sum is the same as the sum of the transposes", we should get the same value for 2([C]T) as we get for (2[C])T. That means the relative precedence is unimportant.
Figure 05
Figure 05 just demonstates a sightly more complex expression.
Figure 06
The two results shown in Figure 06 demonstrate that scalar multiplication distributes over addition.


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©Roger M. Palay     Saline, MI 48176     March, 2017