Consider the matrix . Which of the following statements is true?
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
- A matrix is symmetric if for all .
- Check the off‑diagonal entries: and , which are equal.
- Since the diagonal entries are and , the matrix equals its transpose, so it is symmetric.
- 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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