释义 |
Matrix MultiplicationThe product of two Matrices and is defined by
 | (1) |
where is summed over for all possible values of and . Therefore, in order for multiplication to be defined, thedimensions of the Matrices must satisfy
 | (2) |
where denotes a Matrix with rows and columns. Writing out the product explicitly,
 | (3) |
where
Matrix multiplication is Associative, as can be seen by taking
 | (4) |
Now, since , , and are Scalars, use the Associativity of Scalar Multiplication to write
 | (5) |
Since this is true for all and , it must be true that
 | (6) |
That is, matrix multiplication is Associative. However, matrix multiplication is not, in general,Commutative (although it is Commutative if and are Diagonal andof the same dimension).
The product of two Block Matrices is given by multiplying each block  | |  | | | (7) | See also Matrix, Matrix Addition, Matrix Inverse, Strassen Formulas References
Arfken, G. Mathematical Methods for Physicists, 3rd ed. Orlando, FL: Academic Press, pp. 178-179, 1985.
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