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BITSAT2013MathematicsVector AlgebraActual

If a , b , c are three unit vectors such that a + b + c = 0 , where 0 is null vector, then a b + b c + c a is :

Options

  1. A-3
  2. B-2
  3. C- 3 2
  4. D0

Correct answer

C. - 3 2

Step-by-step solution

We have a + b + c = 0 | a + b + c |=0 | a + b + c |²=0 | a |²+| b |²+| c |²+2( a b + b c + c a )=0 1+1+1+2( a b + b c + c a )=0 a b + b c + c a =- 3 2

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