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AP EAMCET202021 Sep 2020Morning ShiftMathematicsThree Dimensional GeometryActual

The direction cosines of the vector ( a =-2 i + j -5 k ) are

Options

  1. A( -2 8 , 1 8 , -5 8 )
  2. B( -2 30 , 1 30 , -5 30 )
  3. C( 2 8 , -1 8 , 5 8 )
  4. D( -2 30 , -1 30 , -5 30 )

Correct answer

B. ( -2 30 , 1 30 , -5 30 )

Step-by-step solution

The direction cosines of vector ( a =-2 i + j -5 k ) are (- 2 | a | , 1 | a | , -5 | a | ) ( | a |= 4+1+25 = 30 ) ( ) Required direction cosines are (- 2 30 , 1 30 ,- 5 30 ) Hence, option (b) is correct.

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