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Consider the matrix . Which of the following statements is true?

easy MCQ 1 mark Class 12 · Mathematics · Matrices
  1. A is symmetric
  2. A is skew-symmetric
  3. A is orthogonal
  4. A is singular
Answer
A is symmetric

The correct answer is A is symmetric — The matrix is not skew‑symmetric because , not orthogonal because , and its determinant , so it is not singular.

Step-by-step solution

  1. A matrix is symmetric if for all .
  2. Check the off‑diagonal entries: and , which are equal.
  3. Since the diagonal entries are and , the matrix equals its transpose, so it is symmetric.
  4. The matrix is not skew‑symmetric because , not orthogonal because , and its determinant , so it is not singular.
Common mistake: Confusing symmetric with skew‑symmetric (sign of off‑diagonal entries).

Concept tested: Symmetric matrix test

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