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KCET2016MathematicsVector Algebra

Suppose ( a + b + c =0,| a |=3,| b |=5,| c |=7 ), then the angle between ( a & b ) is

Options

  1. A( )
  2. B( 2 )
  3. C( 3 )
  4. D( 4 )

Correct answer

C. ( 3 )

Step-by-step solution

Given that, a + b + c =0 and | a |=3,| b |=5,| c |=7 Now, a + b =- c So, ( a + b ) ( a + b )=(- c ) (- c ) | a |²+| b |²+2 a b =| c |² 9+25+2(3)(5) =49 = 15 2 3 5 = 1 2 = 3

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