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Matrices. Matrix - a rectangular array of variables or constants in horizontal rows and vertical columns enclosed in brackets. Element - each value in a matrix; either a number or a constant. Dimension - number of rows by number of columns of a matrix.
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Matrix - a rectangular array of variables or constants in horizontal rows and vertical columns enclosed in brackets. Element - each value in a matrix; either a number or a constant. Dimension - number of rows by number of columns of a matrix. **A matrix is named by its dimensions.
Examples: Find the dimensions of each matrix. Dimensions: 3x2 Dimensions: 4x1 Dimensions: 2x4
Different types of Matrices • Column Matrix - a matrix with only one column. • Row Matrix - a matrix with only one row. • Square Matrix - a matrix that has the same number of rows and columns.
Equal Matrices - two matrices that have the same dimensions and each element of one matrix is equal to the corresponding element of the other matrix. *The definition of equal matrices can be used to find values when elements of the matrices are algebraic expressions.
Examples: Find the values for x and y * Since the matrices are equal, the corresponding elements are equal! * Form two linear equations. * Solve the system using substitution.
2. Set each element equal and solve!
Matrix Operations • Addition • Subtraction • Multiplication • Inverse
Addition Conformability To add two matrices A and B: • # of rows in A = # of rows in B • # of columns in A = # of columns in B
Subtraction Conformability • To subtract two matrices A and B: • # of rows in A = # of rows in B • # of columns in A = # of columns in B
Multiplication Conformability • Regular Multiplication • To multiply two matrices A and B: • # of columns in A = # of rows in B • Multiply: A (m x n) by B (n by p)
Inner Product of a Vector • (Column) Vector c (n x 1)
Outer Product of a Vector • (Column) vector c (n x 1)
Inverse of 2 x 2 matrix • Find the determinant = (a11 x a22) - (a21 x a12) For det(A) = (2x3) – (1x5) = 1
Inverse of 2 x 2 matrix • Swap elements a11 and a22 Thus becomes
Inverse of 2 x 2 matrix • Change sign of a12 and a21 Thus becomes
Inverse of 2 x 2 matrix • Divide every element by the determinant Thus becomes (luckily the determinant was 1)
Inverse of 2 x 2 matrix • Check results with A-1 A = I Thus equals