AP EAMCET · Maths · Vector Algebra
a, b and \(\mathbf{c}\) are three unit vectors such that no two of them are collinear. If \(\mathbf{b}=2\{\mathbf{a} \times(\mathbf{b} \times \mathbf{c})\}\) and \(\alpha\) is the angle between \(\mathbf{a}, \mathbf{c}\) and \(\beta\) is the angle between \(\mathbf{a}, \mathbf{b}\), then \(\cos (\alpha+\beta)=\)
- A \(\frac{\sqrt{3}}{2}\)
- B \(-\frac{\sqrt{3}}{2}\)
- C \(\frac{1}{2}\)
- D \(-\frac{1}{2}\)
Answer & Solution
Correct Answer
(B) \(-\frac{\sqrt{3}}{2}\)
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