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AP EAMCET202418 May 2024Morning ShiftMathematicsVector AlgebraActual

Let a , b be two unit vector. If c = a +2 b and d =5 a -4 b are perpendicular to each other, then the angle between a and b is

Options

  1. A6
  2. B4
  3. C3
  4. D8

Correct answer

C. 3

Step-by-step solution

Since, | a |=| b |-1 c d =0 ( a +2 b ) (5 a -4 b )=0 aligned & 5| a |^2-4 a b +10 a b -8| b |^2=0 & 5+6 a b -8=0 6 a b =3 aligned | a || b | = 1 2 = 1 2 = 3

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