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KCET2021MathematicsVector Algebra

A vector a makes equal acute angles on the coordinate axis. Then the projection of vector b =5 i +7 j + k on a is

Options

  1. A11 15
  2. B11 3
  3. C4 5
  4. D3 5 3

Correct answer

B. 11 3

Step-by-step solution

Let the equal angles of a with the coordinate axis be . aligned &l= , m= , n= & l²+m²+n² 1 aligned aligned & 3 ² =1 & = 1 3 aligned Direction ratios are 1,1,1 . a = i + j + k Projection of b on a = b a | a | aligned &= (5 i +7 j - k ) ( i + j + k ) 1²+1²+1² &= 5+7-1 3 &= 11 3 aligned

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