An ORTHOGONAL matrix A satisfies:
A$A + A^T = 0$ (skew-symmetric)
B$A^T A = I$ (transpose equals inverse)
C$\det(A) = 0$ (singular always)
D$A^2 = I$ (involution always)
Answer & Solution
Correct answer: B. $A^T A = I$ (transpose equals inverse)
Orthogonal: A^T A = I, so A^(-1) = A^T. Determinant = ±1. Used for rotations and reflections (preserve length + angle).
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