Exercise · ZW-ORTHOGONAL-PROJECTION-002 · ★☆☆ Basic
Compute the orthogonal projection of \(u=(2,3)\) onto \(v=(1,1)\).
Choose one option.
A \(\left(\tfrac52,\tfrac52\right)\) B \((5,5)\) C \(\left(\tfrac52,0\right)\) D \((1,1)\)
Show answer A. \(\left(\tfrac52,\tfrac52\right)\)
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Explanation \(u\cdot v=5\) and \(v\cdot v=2\), so the projection is \(\tfrac52(1,1)\). Forgetting to divide by \(v\cdot v\) gives \((5,5)\).
The orthogonal projection of a vector onto a nonzero vector is the multiple of the latter closest to the former; the remainder is perpendicular to the latter.
\[\operatorname{proj}_{v}u=\frac{u\cdot v}{v\cdot v}\,v\]
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