Class CBSE Class 12 Mathematics Matrices and Determinants Q #736
KNOWLEDGE BASED
APPLY
1 Marks 2024 MCQ SINGLE
If A and B are two skew symmetric matrices, then \((AB+BA)\) is :
(A) a skew symmetric matrix
(B) a symmetric matrix
(C) a null matrix
(D) an identity matrix

AI Tutor Explanation

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Step-by-Step Solution

Let A and B be skew-symmetric matrices. This means that \(A^T = -A\) and \(B^T = -B\).

We want to determine if \(AB + BA\) is symmetric or skew-symmetric. To do this, we will find the transpose of \(AB + BA\).

\((AB + BA)^T = (AB)^T + (BA)^T\)

Using the property that \((XY)^T = Y^T X^T\), we have:

\((AB)^T = B^T A^T\) and \((BA)^T = A^T B^T\)

So, \((AB + BA)^T = B^T A^T + A^T B^T\)

Since A and B are skew-symmetric, \(A^T = -A\) and \(B^T = -B\). Substituting these into the equation:

\((AB + BA)^T = (-B)(-A) + (-A)(-B)\)

\((AB + BA)^T = BA + AB\)

\((AB + BA)^T = AB + BA\)

Since \((AB + BA)^T = AB + BA\), the matrix \(AB + BA\) is symmetric.

Correct Answer: a symmetric matrix

AI Suggestion: Option B

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Pedagogical Audit
Bloom's Analysis: This is an APPLY question because the student needs to apply the properties of skew-symmetric matrices and matrix operations to determine the nature of the resulting matrix (AB+BA).
Knowledge Dimension: CONCEPTUAL
Justification: The question requires understanding the concepts of skew-symmetric matrices and matrix algebra, rather than just recalling facts or following a specific algorithm.
Syllabus Audit: In the context of CBSE Class 12, this is classified as KNOWLEDGE. The question directly tests the properties of matrices as defined in the textbook.