If and are any three vectors forming a linearly independent system

MATHEMATICS · Single correct · CBSE · Mathematics · Vector Algebra · Vector Algebra

Problem

If a,b\mathbf{a}, \mathbf{b} and c\mathbf{c} are any three vectors forming a linearly independent system, then ∀θ∈R\forall \theta \in \mathbb{R}, [acos⁡θ+bsin⁡θ+ccos⁡2θ,acos⁡(2π3+θ)+bsin⁡(2π3+θ)+ccos⁡2(2π3+θ),acos⁡(θ−2π3)+bsin⁡(θ−2π3)+ccos⁡2(θ−2π3)]\left[ \mathbf{a} \cos \theta + \mathbf{b} \sin \theta + \mathbf{c} \cos 2\theta, \mathbf{a} \cos\left(\frac{2\pi}{3} + \theta\right) + \mathbf{b} \sin\left(\frac{2\pi}{3} + \theta\right) + \mathbf{c} \cos 2\left(\frac{2\pi}{3} + \theta\right), \mathbf{a} \cos\left(\theta - \frac{2\pi}{3}\right) + \mathbf{b} \sin\left(\theta - \frac{2\pi}{3}\right) + \mathbf{c} \cos 2\left(\theta - \frac{2\pi}{3}\right) \right] is equal to (1) [abc]cos⁡θ[\mathbf{a} \mathbf{b} \mathbf{c}] \cos \theta (2) [abc]cos⁡2θ[\mathbf{a} \mathbf{b} \mathbf{c}] \cos 2\theta (3) [abc]cos⁡3θ[\mathbf{a} \mathbf{b} \mathbf{c}] \cos 3\theta (4) None of the above

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