If and are two vectors and angles between them is

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

Problem

If a\mathbf{a} and b\mathbf{b} are two vectors and angles between them is θ\theta , then (1) ∣a×b∣2+(a⋅b)2=∣a∣2∣b∣2|\mathbf{a} \times \mathbf{b}|^2 + (\mathbf{a} \cdot \mathbf{b})^2 = |\mathbf{a}|^2 |\mathbf{b}|^2 (2) ∣a×b∣=(a⋅b)|\mathbf{a} \times \mathbf{b}| = (\mathbf{a} \cdot \mathbf{b}) , if θ=π/4\theta = \pi/4 (3) a×b=(a⋅b)n^\mathbf{a} \times \mathbf{b} = (\mathbf{a} \cdot \mathbf{b})\hat{\mathbf{n}} (where n^\hat{\mathbf{n}} is a normal unit vector), if θ=π/4\theta = \pi/4 (4) ∣a×b∣⋅(a+b)=0|\mathbf{a} \times \mathbf{b}| \cdot (\mathbf{a} + \mathbf{b}) = 0

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