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KCET2016MathematicsVector Algebra

If ( a ) and ( b ) are unit vectors then what is the angle between ( a ) and ( b ) for ( 3 a - b ) to be unit vector?

Options

  1. A( 30^ )
  2. B( 45^ )
  3. C( 60^ )
  4. D( 90^ )

Correct answer

A. ( 30^ )

Step-by-step solution

Given that, | a |=| b |=1 and and ( 3 a - b ) ( 3 a - b )=1 3| a |²+| b |²-2 3 a b =1 3+1-2 3 =1 = 3 2 3 = 3 2 =30^

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