Consider the ellipse x29+ y24=1. Let S(p,q) be a point in the first quadrant such that p29+ q24>1. Two tangents are drawn from S to the ellipse, of which one meets the ellipse at one end point of the minor axis and the other meets the ellipse at a point T in the fourth quadrant. Let R be the vertex of the ellipse with positive x-coordinate and O be the center of the ellipse. If the area of the triangle ORT is 32, then which of the following options is correct?
- q=2, p=3 3
- q=2, p=4 3
- q=1, p=5 3
- q=1, p=6 3
Answer
(1) q=2, p=3 3
Solution
S is in the first quadrant, so the tangent at an end of the minor axis is y=2, giving q=2.
R=(3,0); area ORT= 12 3 |yT|= 32 yT=-1
T=(3 ,2 ) with =- 12, = 32, i.e. T= ( 3 32,-1 )
Tangent at T: x3 32- y4=1
Put y=2: 3x6= 32 x=3 3=p
Answer: (A)