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      <text>22.3.2.7 Orthogonal vectors</text>
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<h4>Key Point</h4>
<p>Two \(n\times 1\) column vectors \(X\) and \(Y\) are <strong>orthogonal</strong> if \(X^TY=\mathbf{0}\) or (equivalently) \(Y^TX=\mathbf{0}\).</p>
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