Question Details

Let  P ( x1 , y1 ) and Q ( x2 , y2 ) be two distinct points on the ellipse x2 9 + y2 4 = 1  such that  y1 > 0  and  y2 > 0 .
Let  C  denote the circle  x2 + y2 = 9 , and  M  be the point ( 3 , 0 ) . Suppose the line x = x1  intersects  C  at  R , and

the line x = x2 intersects C at S , such that the y-coordinates of  R  and  S  are positive. Let  ∠ R O M = π 6 and  S O M = π 3 , where  O  denotes the origin ( 0 , 0 ) . Let | X Y | denote the length of the line segment X Y .
Then which of the following statements is (are) TRUE?

Options

A

The equation of the line joining P and Q  is  2x + 3y = 3 ( 1 + 3 )

B

The equation of the line joining  P  and  Q  is 2x + y = 3 ( 1 + 3 )

C

If  N 2 = ( x = 0 ) , then  3 | N 2 Q | = 2 | N 2 S |


D

If  N 1 = ( x = 0 ) , then 9 | N 1 P | = 4 | N 1 R |

Show Answer

Correct Answer :

Option C

If  N 2 = ( x = 0 ) , then  3 | N 2 Q | = 2 | N 2 S |


Option A

The equation of the line joining P and Q  is  2x + 3y = 3 ( 1 + 3 )

Solution :

We are given:
The equation of the ellipse is:

x29+y24=1

Here, the semi-major axis is a = 3 and the semi-minor axis is b = 2.
The auxiliary circle of this ellipse is:

C:x2+y2=9

Let the points R and S lie on the auxiliary circle C such that their y-coordinates are positive. We are given the angles:

ROM=π6 and SOM=π3

where O is the origin (0, 0) and M is the point (3, 0) on the positive x-axis.
Therefore, the coordinates of R and S are:

R=3cosπ6,3sinπ6=332,32

S=3cosπ3,3sinπ3=32,332

The vertical line x=x1 passes through R, which gives:

x1=332

Similarly, the vertical line x=x2 passes through S, which gives:

x2=32

Since P and Q lie on the ellipse with positive y-coordinates (y1>0,y2>0), their coordinates can be written in terms of the eccentric angles of the auxiliary points:

P=3cosπ6,2sinπ6=332,1

Q=3cosπ3,2sinπ3=32,3

Step 1: Check the equation of the line joining P and Q
The slope of the line joining P and Q is:

m=3-132-332=2(3-1)3(1-3)=-23

Using the point-slope form with P:

y-1=-23x-332

3(y-1)=-2x+33

2x+3y=3+33=3(1+3)

Thus, the equation of the line joining P and Q is indeed 2x+3y=3(1+3). This statement is TRUE.

Step 2: Check the statement involving N2
Here, N2 denotes the line x=0 (the y-axis). Let N2Q and N2S denote the distances from the y-axis to the points Q and S along their respective y-coordinates (which corresponds to their y-coordinates):

|N2Q|=yQ=3

|N2S|=yS=332

Evaluating the expression:

3|N2Q|=33

2|N2S|=2332=33

Therefore, 3|N2Q|=2|N2S| is TRUE.

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