Physics I / Dot Product, Cross Product, and Applications
Practice question · Multiple choice

The dot product vanishes for perpendicular vectors and the cross product vanishes for parallel ones. Why are the two conditions opposite?

Hints
  1. Ask what each product is geometrically measuring.
  2. One is about alignment; the other is about spread.
Show the answer

D. Because the dot measures the shared component and the cross the area

Why

Alignment and spread are complementary. That is why the two vanishing conditions are opposite, and why cos\cos and sin\sin appear where they do.

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