NCERT Class XI Mathematics - Conic Sections - Solutions

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Question : 49
Total: 71
y2
9
−
x2
27
= 1
Solution:  
Given equation of hyperbola is
y2
9
−
x2
27
= 1 which is of the form
y2
a2
−
x2
b2
= 1.
The foci and vertices of the hyperbola lie on y-axis.
Now, a2 = 9 ⇒ a = 3 and b2 = 27 ⇒ b = 3 √3
Also, c2 = a2+b2 = 9 + 27 = 36 ⇒ c = 6
So, coordinates of foci are (0, ±c) i.e. (0, ±6)
Coordinates of vertices are (0, ±a) i.e. (0, ±3)
Eccentricity (e) =
c
a
=
6
3
= 2
Length of latus rectum =
2b2
a
=
2×27
3
= 18.
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