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CUET · MATHS · PYQ PAPER 2025

If \(\hat{a}, \hat{b}\) and \(\hat{c}\) are three units vectors and \(\hat{a}+\hat{b}+\hat{c}=\overrightarrow{0}\), then the angle between \(\hat{a}\) and ( \(-\hat{b}\) ) is

  1. A \(\frac{2 \pi}{3}\)
  2. B \(\frac{\pi}{3}\)
  3. C \(\frac{\pi}{2}\)
  4. D \(\frac{\pi}{6}\)
Verified Solution

Answer & Solution

Correct Answer

(B) \(\frac{\pi}{3}\)

Step-by-step Solution

Detailed explanation

\(\hat{a}+\hat{b}=-\hat{c}\) \((\hat{a}+\hat{b}) \cdot (\hat{a}+\hat{b}) = (-\hat{c}) \cdot (-\hat{c})\) \(\|\hat{a}\|^2+\|\hat{b}\|^2+2(\hat{a} \cdot \hat{b}) = \|\hat{c}\|^2\) \(1+1+2(\hat{a} \cdot \hat{b}) = 1\)…