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KCET2016MathematicsThree Dimensional Geometry

If ( , , ) are the direction cosines of a vector ( a ), then ( 2 + 2 + 2 ) is equal to

Options

  1. A( 12 )
  2. B( 13 )
  3. C( -1 )
  4. D( 00 )

Correct answer

C. ( -1 )

Step-by-step solution

We know that, 2 =2 ² -1 So, 2 + 2 + 2 =2 ( ² + ² + ² )-3 Since, , , are the direction cosines of a vector a Then, ² + ² + ² =1 Therefore, 2 + 2 + 2 =2(1)-3=-1

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