alleryFor an orthogonal matrix Q, Q·Qᵀ equals:
AQ
BQᵀ
CI (identity)
D-I
Answer & Solution
Correct answer: C. I (identity)
**Orthogonal matrix:** Q·Qᵀ = Qᵀ·Q = I. Equivalently Q⁻¹ = Qᵀ.
**Important property:** orthogonal matrices preserve lengths and angles (rotations and reflections).
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