{"id":5937,"date":"2021-10-04T15:49:14","date_gmt":"2021-10-04T10:19:14","guid":{"rendered":"https:\/\/mathemerize.com\/?p=5937"},"modified":"2021-11-26T20:32:45","modified_gmt":"2021-11-26T15:02:45","slug":"idempotent-matrix","status":"publish","type":"post","link":"https:\/\/mathemerize.com\/idempotent-matrix\/","title":{"rendered":"Idempotent Matrix – Definition and Example"},"content":{"rendered":"
Here you will learn what is idempotent matrix with examples.<\/p>\n
Let’s begin –<\/p>\n
\nA square matrix is idempotent matrix provided \\(A^2\\) = A.<\/p>\n
For this matrix note the following :<\/p>\n
(i) \\(A^n\\) = A \\(\\forall\\) n \\(\\ge\\) 2, n \\(\\in\\) N.<\/p>\n
(ii) The determinant value of this matrix is either 1 or 0.<\/p>\n<\/blockquote>\n
Example<\/span><\/strong> : Show that the matrix A = \\(\\begin{bmatrix} 2 & -2 &\u00a0 -4 \\\\\u00a0 -1 & 3 & 4 \\\\\u00a0 1 & -2 & -3 \\end{bmatrix}\\) is idempotent.<\/p>\n
Solution<\/span><\/strong> : We have,<\/p>\n
A = \\(\\begin{bmatrix} 2 & -2 &\u00a0 -4 \\\\\u00a0 -1 & 3 & 4 \\\\\u00a0 1 & -2 & -3 \\end{bmatrix}\\)<\/p>\n
Now, \\(A^2\\) = A.A<\/p>\n
\\(\\implies\\) A = \\(\\begin{bmatrix} 2 & -2 &\u00a0 -4 \\\\\u00a0 -1 & 3 & 4 \\\\\u00a0 1 & -2 & -3 \\end{bmatrix}\\) \\(\\times\\) \\(\\begin{bmatrix} 2 & -2 &\u00a0 -4 \\\\\u00a0 -1 & 3 & 4 \\\\\u00a0 1 & -2 & -3 \\end{bmatrix}\\)<\/p>\n
= \\(\\begin{bmatrix} 2 & -2 &\u00a0 -4 \\\\\u00a0 -1 & 3 & 4 \\\\\u00a0 1 & -2 & -3 \\end{bmatrix}\\) = A<\/p>\n
Hence, matrix A is idempotent.<\/p>\n
Example<\/span><\/strong> : Find the determinant of above matrix A = \\(\\begin{bmatrix} 2 & -2 &\u00a0 -4 \\\\\u00a0 -1 & 3 & 4 \\\\\u00a0 1 & -2 & -3 \\end{bmatrix}\\)<\/p>\n
Solution<\/span><\/strong> : We have,<\/p>\n
A = \\(\\begin{bmatrix} 2 & -2 &\u00a0 -4 \\\\\u00a0 -1 & 3 & 4 \\\\\u00a0 1 & -2 & -3 \\end{bmatrix}\\)<\/p>\n
Now, | A | = \\(\\begin{vmatrix} 2 & -2 &\u00a0 -4 \\\\\u00a0 -1 & 3 & 4 \\\\\u00a0 1 & -2 & -3 \\end{vmatrix}\\)<\/p>\n
\\(\\implies\\) | A | = 2 \\(\\begin{vmatrix} 3 & 4 \\\\ -2 & -3 \\end{vmatrix}\\) – (-2) \\(\\begin{vmatrix} -1 & 4 \\\\\u00a0 1 & -3 \\end{vmatrix}\\) + (-4) \\(\\begin{vmatrix}\u00a0 -1 & 3 \\\\\u00a0 1 & -2 \\end{vmatrix}\\)<\/p>\n
\\(\\implies\\) | A | = 2 (-9 + 8) + 2 (3 – 4) – 4 ( 2 – 3)\u00a0<\/p>\n
= 2(-1) + 2(-1) – 4(-1)<\/p>\n
= -2 –\u00a0 2 + 4 = 0<\/p>\n
Hence, determinant of matrix A is 0.<\/p>\n\n\n