If a and b are two unit vectors such that a +2 b and 5 a -4 b are perpendicular to each…
Mathematics · JEE Main · NTA Exams — Vector Algebra
If \(\scriptstyle{\vec{\mathbf{a}}}\,\mathbf{and}\,{\vec{\mathbf{b}}}\) are two unit vectors such that \(\vec{a}+2 \vec{b} \text { and } 5 \vec{a}-4 \vec{b}\) are perpendicular to each other then the angle between \(\scriptstyle{\vec{\mathbf{a}}}\,\mathbf{and}\,{\vec{\mathbf{b}}}\) is :
- 45°
- 60°
- \(\cos ^{-1}\left(\frac{1}{3}\right)\)
- \(\cos -1\left(\frac{2}{7}\right)\)
Answer
(B) 60 °
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