The volume of the parallelopiped whose coterminous edges are represented by the vectors

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

Problem

The volume of the parallelopiped whose coterminous edges are represented by the vectors 2b×c2\mathbf{b} \times \mathbf{c} , 3c×a3\mathbf{c} \times \mathbf{a} and 4a×b4\mathbf{a} \times \mathbf{b} where a=(1+sin⁡θ)i^+cos⁡θj^+sin⁡2θk^\mathbf{a} = (1 + \sin \theta)\hat{\mathbf{i}} + \cos \theta \hat{\mathbf{j}} + \sin 2\theta \hat{\mathbf{k}} b=sin⁡(θ+2π3)i^+cos⁡(θ+2π3)j^+sin⁡(2θ+4π3)k^,\mathbf{b} = \sin\left(\theta + \frac{2\pi}{3}\right)\hat{\mathbf{i}} + \cos\left(\theta + \frac{2\pi}{3}\right)\hat{\mathbf{j}} + \sin\left(2\theta + \frac{4\pi}{3}\right)\hat{\mathbf{k}}, c=sin⁡(θ−2π3)i^+cos⁡(θ−2π3)j^+sin⁡(2θ−4π3)k^ is 18\mathbf{c} = \sin\left(\theta - \frac{2\pi}{3}\right)\hat{\mathbf{i}} + \cos\left(\theta - \frac{2\pi}{3}\right)\hat{\mathbf{j}} + \sin\left(2\theta - \frac{4\pi}{3}\right)\hat{\mathbf{k}} \text{ is 18} cubic units, then the value of θ\theta in the interval [0,π2]\left[0, \frac{\pi}{2}\right] , is/are (1) π9\frac{\pi}{9} (2) 2π9\frac{2\pi}{9} (3) π3\frac{\pi}{3} (4) 4π9\frac{4\pi}{9}

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