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Question : 56 of 160
Marks:
+1 ,
-0
Solution:
Given, ellipse
3 x 2 + 4 y 2 = 12 ⇒ ‌ + ‌ = 1 e = √ 1 − ‌ = √ ‌ = ‌ Latus rectums
x = ± a e = ± ( 2 ) ( ‌ ) = ± 1 ∵ L 1 ′ is the end of a latus rectum and it is lying in the third quadrant
∵ ‌ ‌ L 1 ′ = ( − 1 , − √ 3 ( 1 − ‌ ) ) = ( − 1 , − ‌ ) Equation tangent at
( − 1 , ‌ ) is given by
‌ + ‌ = 1 ⇒ x + 2 y + 4 = 0 Slope of tangent
= − ‌ ∴ Slope of normal
= − ( ‌ ) = 2 . Equation of normal from
( − 1 , − ‌ ) is given by
y + ‌ = 2 ( x + 1 ) ⇒ 4 x − 2 y + 1 = 0 The points of intersection of the normal
4 x − 2 y + 1 = 0 and the ellipse
‌ + ‌ = 1 are
L 1 ′ ( − 1 , − ‌ ) ‌ and ‌ P ( ‌ , ‌ ) Hence,
a = ‌
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