4.1.1 Matrices and Data Key Objectives
• Use matrices to display mathematical and real-world data. • Find sums, differences, and scalar products of matrices. Key Terms • A matrix is a rectangular array of numbers enclosed in brackets. • The dimensions of a matrix are the size and shape of the matrix, given by the number of rows by the number of columns of the matrix, written as rows × columns. • An entry is a value in a matrix; also called an element. • An address is the location of an entry in a matrix, given by the row and column in which the entry appears. In matrix A , the address of the entry in row i and column j is a ij . • A scalar is a number that is multiplied by a matrix. • A scalar product is the product of multiplying a number, called a scalar, by a matrix. Example 1 Matrices and Data In matrices and tables, the number of rows is equal to the number of entries listed horizontally and the number of columns is equal to the number of entries listed vertically.
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