mckenzievitch2900 mckenzievitch2900 20-02-2024 Mathematics contestada 9. Show that if \( \theta \) is the angle between \( A \) and \( B \), then \[ \|A-B\|^{2}=\|A\|^{2}+\|B\|^{2}-2\|A\|\|B\| \cos \theta \text {. } \]
