NCERT Class XI Mathematics - Conic Sections - Solutions

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Question : 52
Total: 71
5y29x2 = 36
Solution:  
Given equation of hyperbola is 5y29x2 = 36
i.e.,
5y2
36
9x2
36
= 1 ⇒
y2
36
5
x2
4
= 1,
which is of the form
y2
a2
x2
b2
= 1.
The foci and vertices of the hyperbola lie on y-axis.
Now, a2 =
36
5
⇒ a =
6
5
and b2 = 4 ⇒ b = 2
Also, x2 = a2+b2 =
36
5
+4
=
56
5
⇒ c =
56
5
= 2
14
5

∴ Coordinates of foci are (0, ± c) i.e. (0,±
214
5
)

Coordinates of vertices are (0, ± a) i.e. (0,±
6
5
)

Eccentricity (e) =
c
a
=
2
14
5
6
5
=
14
3

Length of latus rectum =
2b2
a
=
2×4
6
5
=
45
3
.
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