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JEE Main201912 Jan 2019Evening ShiftMathematicsCircleActual

If a circle of radius R passes through the origin O and intersects the coordinate axes at A and B , then the locus of the foot of perpendicular from O on A B is :

Options

  1. Ax 2 + y 2 x + y = R 2 x y
  2. Bx 2 + y 2 3 = 4 R 2 x 2 y 2
  3. Cx 2 + y 2 2 = 4 R 2 x 2 y 2
  4. Dx 2 + y 2 2 = 4 R x 2 y 2

Correct answer

B. x 2 + y 2 3 = 4 R 2 x 2 y 2

Step-by-step solution

Since, circle passing through origin intersect the coordinate axes at A &   B , hence A B must be diameter and A B = 2 R . Now, let foot of the perpendicular from origin upon A B be P h ,   k . Slope of line O P = k - 0 h - 0 = k h Since, line A B ⊥ O P ⇒ slope of A B = - h k Thus, equation of line A B is y - k = - h k x - h For co-ordinates of A , put y = 0 ⇒ 0 - k = - h k x - h ⇒ x = h 2 + k 2 h ⇒ A   h 2 + k 2 h ,   0 . For co-ordinates of B , put x = 0 &#865

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