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COMPOSITION OF MAPPINGS. Matrix Multiplication. Pamela Leutwyler. = the matrix for T. = the matrix for S. R 3. R 2. T. S. R 2. S T. R 3. Find the matrix for ST. R 2. T. S. R 2. S T. The first column of ST is S(the first column of T).
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COMPOSITION OF MAPPINGS Matrix Multiplication Pamela Leutwyler
R3 R2 T S R2 ST
R3 Find the matrix for ST R2 T S R2 ST
One way to define the product of two Matrices A and B is: THE nth COLUMN OF AB IS A( nth COLUMN OF B )
Because the matrix product AB represents a COMPOSITION OF MAPPINGS, It is important that the RANGE OF B is within The DOMAIN OF A. If A is an mn matrix, It has m rows and n columns. Its domain is Rn, and its range is Rm If B is an np matrix, It has n rows and p columns. Its domain is Rp, and its range is Rn We can form the product AB And the answer will be An mp matrix. mn np
Conformable: can be multiplied Consider the example: C D CD 32 24 34
Consider the example: C D CD 32 24 34
Consider the example: C D CD 32 24 34 To find the third column of CD take C times the third column of D
is row 2 of C DOT column 3 of D Consider the example: C D CD 1 32 24 34 To break this down further, consider the second entry in column 3 the entry in row 2 column 3 of CD
In general, for any two conformable matrices A and B: The entry in row j, column k of AB Is (row j of A) dot (column k of B) column k row j A B AB
Consider the example: C D CD
Consider the example: C D CD
Consider the example: C D CD
Consider the example: C D CD
Consider the example: C D CD
Consider the example: C D CD
Consider the example: C D CD Sorry – I skipped a few steps!
Consider the example: C D CD