NCERT Class XI Mathematics - Conic Sections - Solutions

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Question : 56
Total: 71
Vertices (0, ±3), foci (0, ±5)
Solution:  
Vertices are (0, ±3) which lie on y-axis.
So the equation of hyperbola in standard form is
y2
a2
x2
b2
= 1
Now vertices are (0, ±3) ⇒ a = 3; Co-ordinates of Foci are (0, ±5) ⇒ ae = 5
Now, ae = 5 ⇒ e =
5
a
⇒ e =
5
3

We know that b = ae21 ⇒ b = 3
25
9
1
= 3
16
9
= 4
Thus required equation of hyperbola is
y2
(3)2
x2
(4)2
= 1 ⇒
y2
9
x2
16
= 1.
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