Let T 1 and T 2 be two distinct common tangents to the ellipse E : x 2 6 + y 2 3 = 1 and the parabola P : y…

Let T1 and T2 be two distinct common tangents to the ellipse E:x26+y23=1 and the parabola P:y2=12x. Suppose that the tangent T1 touches P and E at the points A1 and A2, respectively and the tangent T2 touches P and E at the points A4 and A3, respectively. Then which of the following statements is(are) true?
  1. The area of the quadrilateral A1A2A3A4 is 35 square units
  2. The area of the quadrilateral A1A2A3A4 is 36 square units
  3. The tangents T1 and T2 meet the x-axis at the point 3, 0
  4. The tangents T1 and T2 meet the x-axis at the point 6, 0

Solution

Given,

Equation of ellipse

E:x26+y23=1,

Now equation of tangent with slope m1 will be :

T1: y=m1x±6m12+3

And equation of parabola,

P:y2=12x,

So, equation of tangent with slope m2 will be:

y=m2x+3m2

Now for common tangent

m=m1=m2, ±6m12+3=3m2

 m=±1

Hence, equation of common tangents will be,

y=x+3 and y=x-3

Now we know that,

Point of contact for parabola is am2, 2am

 A13, 6, A43-6

Now let A2x1, y1

So, equation of tangent to ellipse E at point A2x1, y1 is given by,

 xx16+yy13=1

Now comparing above equation with y=x+3,

We get, -x16=y13=13

A2-63,33-2,1

Now A3 is mirror image of A2 in x-axis 

A3-2, -1 

Now finding the intersection point of T1=0 and T2=0, we get -3, 0

So, Area of quadrilateral A1A2A3A4=1212+2×5=35 square units

Asked in: JEE Advanced 2023 (Paper 1)

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