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CUET · MATHS · PYQ PAPER 2025

If \(\vec{a}, \vec{b}, \vec{c}\) are vectors such that \(\vec{a}+\vec{b}+\vec{c}=\overrightarrow{0}\) and \(|\vec{a}|=1,|\vec{b}|=2,|\vec{c}|=5\), then the expression \(\vec{a} \cdot \vec{b}+\vec{b} \cdot \vec{c}+\vec{c} \cdot \vec{a}\) equals

  1. A 30
  2. B \(-15\)
  3. C \(0\)
  4. D 1
Verified Solution

Answer & Solution

Correct Answer

(B) \(-15\)

Step-by-step Solution

Detailed explanation

\(|\vec{a}+\vec{b}+\vec{c}|^2 = |\vec{a}|^2 + |\vec{b}|^2 + |\vec{c}|^2 + 2(\vec{a} \cdot \vec{b} + \vec{b} \cdot \vec{c} + \vec{c} \cdot \vec{a})\) \(0^2 = 1^2 + 2^2 + 5^2 + 2(\vec{a} \cdot \vec{b} + \vec{b} \cdot \vec{c} + \vec{c} \cdot \vec{a})\)…
From CUET
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