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AP EAMCET202419 May 2024Evening ShiftMathematicsThree Dimensional GeometryActual

Let a b =7 i -5 j -4 k and a = i +3 j -2 k . If the length of projection of b on a is 8 14 , then | b |=

Options

  1. A121
  2. B12
  3. C11
  4. D144

Correct answer

C. 11

Step-by-step solution

Since, length of projection of b on a is 8 14 | a b | | a | = 8 14 Now, a b = a b | a | = 7 i -5 j -4 k 1+9+4 = 7 i -5 j -4 k 14 Since, | a b |^2+| a b |^2=| b |^2| a |^2 | b |^2= 154 14 | b |= 11

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