Practice question · Multiple choice
A recommender compares users by the cosine of the angle between their rating vectors rather than Euclidean distance. What problem does that solve?
Hints
- Two users rank the same films in the same order; one rates everything two stars higher. Compare their vectors.
- Ask which measure calls those users similar.
Show the answer
C. Generous and harsh raters get vectors pointing the same way
Why
One user's vector is essentially a scaled version of the other's — same direction, greater magnitude — so the angle says 'identical taste' and the distance says 'far apart'. Magnitude here encodes generosity rather than preference, and cosine is the decision to ignore it.
Practise Dot Product and Orthogonality
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