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COMEDK2023MathematicsVector Algebra

The angle between the vectors a = i +2 j +2 k and b = i +2 j -2 k is

Options

  1. A⁻¹(1 / 9)
  2. B⁻¹(8 / 9)
  3. C⁻¹(8 / 9)
  4. D⁻¹(1 / 9)

Correct answer

D. ⁻¹(1 / 9)

Step-by-step solution

We have, a = i +2 j +2 k and b = i +2 j -2 k Clearly, | a |= 1+4+4 = 9 =3 array ll and & | b |= 1+4+4 = 9 =3 & a b =|a||b| & = 1 1+2 2+2 (-2) 3 3 & = 1+4-4 9 = 1 9 & = ⁻¹ ( 1 9 ) array

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