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QJEEAdv18Ma5cf0: JEE Advanced 2018 Mathematics - Class 11 JEEAdv18Ma5cf0 Solution: Let S be the circle in the XY-plane defined the equation x 2 +…

Let S be the circle in the XY-plane defined the equation x2 + y2 = 4.

Let E1E2 and F1F2 be the chords of S passing through the point P0 (1, 1) and parallel to the X-axis and the Y-axis, respectively. Let G1G2 be the chord of S passing through P0 and having slope −- 1. Let the tangents to S at E1 and E2 meet at E3, then tangents to S at F1 and F2 meet at F3, and the tangents to S at G1 and G2 meet at G3. Then, the points E3, F3 and G3 lie on the curve

Multiple Choice Options

  • A x + y = 4
  • B (x −- 4)2 + (y −- 4)2 = 16
  • C (x −- 4)(y −- 4) = 4
  • D xy = 4

Step-by-Step Verified Solution

JEE Advanced 2018 Paper 1 Offline Mathematics - Circle Question 12 English Explanation

Equation of tangent at E1(−3,1){E_1}( - \sqrt 3 ,1) is

−3- \sqrt 3 x + y = 4 and at E2(3,1){E_2}(\sqrt 3 ,1) is 3\sqrt 3 x + y = 4

Intersection point of tangent at E1 and E2 is (0, 4)

∴\therefore Coordinates of E3 is (0, 4)

Similarly, equation of tangent at

F1(1,−3){F_1}(1, - \sqrt 3 ) and F2(1,3){F_2}(1,\sqrt 3 ) are x −- 3\sqrt 3 y = 4 and

x + 3\sqrt 3 y = 4, respectively and intersection point
is (4, 0), i.e., F3(4, 0) and equation of tangent at G1(0, 2) and G2(2, 0) are 2y = 4 and 2x = 4, respectively and intersection point
is (2, 2) i.e., G3(2, 2).

Point E3(0, 4), F3(4, 0) and G3(2, 2) satisfies the line x + y = 4.

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