Engineering Fundamentals: An Introduction to Engineering, 4th ed.c

(Steven Felgate) #1

18.5 Matrix Algebra 609


This may be a good place to point out that if [I] is an identity matrix and [A] is a square matrix
of matching size, then it can be readily shown that the product of

(18.13)


Example 18.1 Given matrices: perform


the following operations.


(a) [A] [B] ?
(b) [A] [B] ?
(c) 3[A] ?
(d) [A][B] ?
(e) [A]{C} ?
(f ) Show that [I][A] [A][I] [A]

We will use the operation rules discussed in the preceding sections to answer these
questions.

(a) [A] [B] ?


(b) [A] [B] ?


(c) 3[A] ?


33 A 4  3 £


050


837


9  29


§£


0 132152 0


132182132132132172


1321921321  22132192


§£


01 5 0


24 9 21


27  627


§



10  4215  6210  1  222


18  7213  22 17  32


19  121  2  3219  1  422


§£


 4  12


114


8  513


§


3 A 4  3 B 4 £


050


837


9  29


§£


46  2


72 3


13  4


§



10  4215  6210  1  222


18  7213  2217  32


19  121  2  3219  1  422


SC


 4 11  2


15  5  10


10  1   5


§


3 A 4  3 B 4 £


050


837


9  29


SC


46  2


72 3


13  4


§


3 A 4 £


050


837


9  29


§, 3 B 4 £


46  2


72 3


13  4


§, and 5 C 6 •


 1


2


5


¶,


3 I 43 A 4  3 A 43 I 4  3 A 4


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