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AP EAMCET202023 Sep 2020Morning ShiftMathematicsThree Dimensional GeometryActual

The angle between the lines with direction ratios 2 , - 2 , 1 and 1 , - 2 , 2 is

Options

  1. Acos - 1 4 9
  2. Bcos - 1 8 9
  3. Cπ 6
  4. Dπ 2

Correct answer

B. cos - 1 8 9

Step-by-step solution

Direction ratios are ( 2 , - 2 , 1 ) and ( 1 , - 2 , 2 ) cos θ = 2 × 1 + ( - 2 × - 2 ) + 1 × 2 2 2 + ( - 2 ) 2 + 1 2   1 2 + ( - 2 ) 2 + 2 2 = 8 3 × 3 = 8 9

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