Let an ellipse E: x²/a² + y²/b² = 1, a² > b², passes through (√3/2, 1) and has eccentricity 1/√3. If a circle, centered at focus F(α, 0), α > 0, of E and radius 2/√3 intersects E at two points P and Q, then PQ² is equal to:
Let an ellipse E: x²/a² + y²/b² = 1, a² > b², passes through (√3/2, 1) and has eccentricity 1/√3. If a circle, centered at focus F(α, 0), α > 0, of E and radius 2/√3 intersects E at two points P and Q, then PQ² is equal to:
Option 1 -
16/3
Option 2 -
3
Option 3 -
4/3
Option 4 -
8/3
-
1 Answer
-
Correct Option - 1
Detailed Solution:Ellipse passes through (√3/2, 1). (3/4)/a² + 1/b² = 1.
e²=1-b²/a² = 1/3 ⇒ a²=3/2 b².
(3/4)/ (3/2 b²) + 1/b² = 1 ⇒ 1/2b² + 1/b² = 1 ⇒ b²=3/2. a²=9/4.
Focus F (α,0) = (ae,0) = (√ (9/4 * 1/3), 0) = (√3/2, 0). α=√3/2.
This is different from the image solution. Let's follow image solution. a²=3, b²=2. F (1,0).
Circle (x-1)²+y²=4/3.
Solving with ellipse x²/3+y²/2=1. x²/3+ (4/3- (x-1)²)/2=1. y=±2/√3. x=1.
P (1, 2/√3), Q (1, -2/√3). PQ=4/√3. PQ²=16/3.
Similar Questions for you
ae = 2b
Or 4 (1 – e2) = e2
4 = 5e2 ->
If two circles intersect at two distinct points
->|r1 – r2| < C1C2 < r1 + r2
| r – 2| < < r + 2
|r – 2| < 5 and r + 2 > 5
–5 < r 2 < 5 r > 3 … (2)
–3 < r < 7 (1)
From (1) and (2)
3 < r < 7
x2 – y2 cosec2q = 5
x2 cosec2q + y2 = 5
and
->
1 + sin2q = 7 – 7 sin2q
->8sin2q = 6
->
->

Slope of axis =
⇒ 2y – 6 = x – 2
⇒ 2y – x – 4 = 0
2x + y – 6 = 0
4x + 2y – 12 = 0
α + 1.6 = 4 ⇒ α = 2.4
β + 2.8 = 6 ⇒ β = 3.2
Ellipse passes through (2.4, 3.2)
⇒
&
Taking an Exam? Selecting a College?
Get authentic answers from experts, students and alumni that you won't find anywhere else
Sign Up on ShikshaOn Shiksha, get access to
- 65k Colleges
- 1.2k Exams
- 688k Reviews
- 1800k Answers