{"id":4996,"date":"2021-09-04T00:18:35","date_gmt":"2021-09-03T18:48:35","guid":{"rendered":"https:\/\/mathemerize.com\/?p=4996"},"modified":"2022-01-16T17:01:49","modified_gmt":"2022-01-16T11:31:49","slug":"how-to-find-trace-of-matrix","status":"publish","type":"post","link":"https:\/\/mathemerize.com\/how-to-find-trace-of-matrix\/","title":{"rendered":"How to Find Trace of Matrix – Properties and Example"},"content":{"rendered":"
Here you will learn how to find trace of matrix, its properties and what is orthogonal matrix with example.<\/p>\n
Let’s begin –<\/p>\n
The sum of the elements of the square matrix A lying along the principal diagonal<\/strong> is called the trace of A<\/strong> i.e (tr(A))<\/strong>. <\/p>\n Thus if A = \\([a_{ij}]_{n\\times n}\\),<\/p>\n then tr(A) = \\(\\sum_{i=1}^{n}\\) \\(a_{ii}\\) = \\(a_{11}\\) + \\(a_{22}\\) + ……… + \\(a_{nn}\\).<\/p>\n<\/blockquote>\n How to Find Trace of Matrix :<\/strong><\/p>\n for example, for 3×3 matrix<\/strong>, if A = \\(\\begin{bmatrix} 2 & 1 & -1 \\\\ 3 & -2 & 5 \\\\ 1 & 5 & 3 \\end{bmatrix}\\) <\/p>\n then, trace of A <\/strong>or tr(A)<\/strong> = 2 + (-2) + 3 = 3<\/p>\n for example, for 2×2 matrix<\/strong>, if A = \\(\\begin{bmatrix} 2 & 1 \\\\ 3 & 4 \\end{bmatrix}\\) <\/p>\n then, trace of A <\/strong>or tr(A)<\/strong> = 2 + 4 = 6<\/p>\n Let A = \\([a_{ij}]_{n\\times n}\\) and B = \\([b_{ij}]_{n\\times n}\\) and \\(\\lambda\\) be a scalar then<\/p>\n (i) tr(\\(\\lambda A\\)) = \\(\\lambda\\) tr(A) <\/p>\n (ii) tr(A + B) = tr(A) + tr(B)<\/p>\n (iii) tr(AB) = tr(BA)<\/p>\n<\/blockquote>\n A square matrix is said to be orthogonal matrix if <\/p>\n \\(AA^T\\) = I (Identity matrix)<\/p>\n<\/blockquote>\n Note<\/strong> : The determinant value of orthgonal matrix is 1 or -1.<\/p>\n\n\n Example : <\/span>Show that the matrix A = \\(\\begin{bmatrix} cosx & sinx \\\\ -sinx & cosx \\end{bmatrix}\\) is a orthogonal matrix.<\/p>\n Solution : <\/span>We have,\n
Properties of Trace of a Matrix<\/strong><\/h4>\n
\n
Orthogonal Matrix<\/h2>\n
\n
\nA = \\(\\begin{bmatrix} cosx & sinx \\\\ -sinx & cosx \\end{bmatrix}\\)
\n\\(A^{T}\\) = \\(\\begin{bmatrix} cosx & -sinx \\\\ sinx & cosx \\end{bmatrix}\\)
\nNow, we have to find \\(AA^T\\) = \\(\\begin{bmatrix} cosx & sinx \\\\ -sinx & cosx \\end{bmatrix}\\)\\(\\begin{bmatrix} cosx & -sinx \\\\ sinx & cosx \\end{bmatrix}\\)
\n= \\(\\begin{bmatrix} cos^2x + sin^2x & -cosx.sinx + sinx.cosx \\\\ -sinx.cosx + sinx.cosx & cos^2x + sin^2x \\end{bmatrix}\\)
\n= \\(\\begin{bmatrix} 1 & 0 \\\\ 0 & 1 \\end{bmatrix}\\) = I (Identity matrix)
\n\\(\\implies\\) \\(AA^T\\) = I
\nHence, it is an orthogonal matrix.
<\/p>\n\n\n\n