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AP EAMCET202119 Aug 2021Evening ShiftMathematicsThree Dimensional GeometryActual

If the projections of the line segment A B → on X Y , Y Z and Z X planes are 15 , 46 , 7 respectively, then the projection of A B → on y - axis is

Options

  1. A9
  2. B1
  3. C4
  4. D7

Correct answer

B. 1

Step-by-step solution

Let, the vector A B → = l i ^ + m j ^ + n k ^ Projection on X Y plane is l 2 + m 2 = 15   ⇒   l 2 + m 2 = 15     . . . 1 Projection on Y Z plane is m 2 + n 2 = 46   ⇒   m 2 + n 2 = 46     . . . 2 Projection on Z X plane is n 2 + l 2 = 7 ⇒ n 2 + l 2 = 49     . . . 3 Subtracting equation 2 from equation 3   , l 2 + n 2 - n 2 + m 2 = 49 - 46 = 3   ⇒ l 2 - m 2 = 3 ⇒   l + m l - m = 3   ⇒ l + m = 3 and l - m =

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