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Question: Answered & Verified by Expert
If $\bar{a}$ and $\bar{b}$ are two vectors such that $|\vec{a}|=|\vec{b}|=\sqrt{2}$ with $\vec{a} \cdot \vec{b}=-1$, then the angle between $\bar{a}$ and $\bar{b}$ is
MathematicsVector AlgebraMHT CETMHT CET 2022 (07 Aug Shift 1)
Options:
  • A $\frac{3 \pi}{4}$
  • B $\frac{5 \pi}{6}$
  • C $\frac{5 \pi}{9}$
  • D $\frac{2 \pi}{3}$
Solution:
2025 Upvotes Verified Answer
The correct answer is: $\frac{2 \pi}{3}$
$\theta=\cos ^{-1}\left(\frac{\vec{a} \cdot \vec{b}}{|\vec{a}||\vec{b}|}\right)=\cos ^{-1}\left(\frac{-1}{\sqrt{2} \sqrt{2}}\right)=\cos ^{-1}\left(\frac{-1}{2}\right)=\frac{2 \pi}{3}$

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