Grade 11

Grade 11Vectors and MatricesMatrices


Matrix Operations


Matrices are everywhere in mathematics and are particularly useful in many fields such as physics, computer science and economics. In Grade 11 Mathematics, you begin to delve deeper into these fascinating structures, understanding how they are applied and manipulated through various operations. This page will guide you through the fundamentals of matrix operations in an accessible and comprehensive way.

What is a matrix?

A matrix is essentially a rectangular array of numbers arranged in rows and columns. These numbers are called the elements of the matrix. The size or dimension of a matrix is defined by the number of rows and columns it contains. For example, a matrix with 3 rows and 2 columns would be a 3x2 matrix.

Here's an example:

A = | 1 2 | | 3 4 | | 5 6 |

Here, matrix A is a 3x2 matrix.

Types of matrices

Before delving deeper into the operations, it is important to understand the different types of matrices:

  • Row Matrix: A matrix with only one row. Example:
    R = | 7 8 9 |
  • Column Matrix: A matrix with only one column. Example:
    C = | 1 | | 4 | | 7 |
  • Square matrix: A matrix with the same number of rows and columns. Example:
    Q = | 5 6 | | 7 8 |
  • Diagonal Matrix: A square matrix where all the elements outside the main diagonal are zero. Example:
    D = | 3 0 0 | | 0 5 0 | | 0 0 9 |
  • Identity Matrix: A square matrix where all the elements of the main diagonal are ones, and all other elements are zero. Usually denoted by I Example:
    I = | 1 0 0 | | 0 1 0 | | 0 0 1 |

Addition and subtraction of matrices

Addition and subtraction of matrices are relatively simple operations, but there is an important condition: the matrices to be added or subtracted must be of the same dimension.

Matrix addition

To add two matrices, simply add their corresponding elements. For example:

A = | 2 3 | B = | 4 1 | | 5 7 | | 0 2 | A + B = | (2+4) (3+1) | | (5+0) (7+2) | = | 6 4 | | 5 9 |

Matrix subtraction

To subtract one matrix from another, subtract their corresponding elements. For example:

A = | 6 4 | B = | 1 3 | | 2 5 | | 4 7 | A - B = | (6-1) (4-3) | | (2-4) (5-7) | = | 5 1 | |-2 -2 |

Scalar multiplication

Scalar multiplication involves multiplying each element of a matrix by a scalar (real number). For example:

k = 3, A = | 2 1 | | 3 4 | kA = | 3*2 3*1 | | 3*3 3*4 | = | 6 3 | | 9 12 |

Matrix multiplication

Matrix multiplication is a little more complicated than addition, subtraction, or scalar multiplication. Two matrices can be multiplied only if the number of columns in the first matrix is equal to the number of rows in the second matrix.

For example, consider two matrices A and B where:

A = | 3 4 2 | a 1x3 matrix B = | 13 9 7 15| b 3x4 matrix | 8 7 4 6 | | 6 4 0 3 | Resultant Matrix C, where C = A x B, would be of size 1x4.

To calculate the element in the ith row and jth column of a matrix product A x B , perform the dot product of the ith row of A and the jth column of B For the first element you do it like this:

C11 = (3 * 13) + (4 * 8) + (2 * 6) = 39 + 32 + 12 = 83

Compute all the elements in this manner to obtain the resultant matrix C

Transposing a matrix

The transpose of a matrix is formed by swapping its rows with its columns and vice versa. The transpose of a matrix A is usually denoted as A T

For example, if:

A = | 3 7 | | 5 6 | | 8 9 |

Then, the transpose of A is:

A T = | 3 5 8 | | 7 6 9 |

Identity matrix and inverse matrix

The identity matrix for multiplication is like the number 1 for multiplying the numbers. The identity matrix I is a square matrix in which all diagonal elements are equal to one and other elements are equal to zero.

Inverse matrix

Only square matrices have an inverse, and not all square matrices have an inverse. If it exists, then the inverse of the matrix A is the matrix A -1 , such that:

A * A -1 = I

where I is the identity matrix.

Conclusion

Understanding matrix operations is a fundamental aspect of dealing with matrices. These operations form the backbone for more complex mathematical functions and are essential tools in many scientific analyses.

Feel encouraged to practice with different matrices to solidify your understanding of these operations. Over time, the concepts will become intuitive as you become more comfortable with the math associated with matrices.


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