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JEE Mains · Maths · STD 12 - 10. vector algebra

Let a vector \( \overrightarrow{a}=\sqrt{2i}-\hat{j}+\lambda\hat{k}, \lambda>0, \) make an obtuse angle with the vector \( \overrightarrow{b}=-\lambda^{2}\hat{i}+4\sqrt{2j}+4\sqrt{2}\hat{k} \) and an angle \( \theta, \frac{\pi}{6}<\theta<\frac{\pi}{2} \) with the positive z-axis. If the set of all possible values of \( \lambda \) is \( (\alpha,\beta)-\{\gamma\} \), then \( \alpha+\beta+\gamma \) is equal to ___ .

  1. A 5
  2. B 4
  3. C 6
  4. D 7
Verified Solution

Answer & Solution

Correct Answer

(A) 5

Step-by-step Solution

Detailed explanation

\(\frac{\overrightarrow{ a } \cdot \hat{ k }}{|\overrightarrow{ a }|}=\cos \theta \Rightarrow \frac{\lambda}{\sqrt{3+\lambda^2}}=\cos \theta\) \(\Rightarrow 0<\frac{\lambda}{\sqrt{3+\lambda^2}}<\frac{\sqrt{3}}{2}\)…