NCERT Class XI Mathematics - Conic Sections - Solutions

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Question : 55
Total: 71
Vertices (0, ±5), foci (0, ±8)
Solution:  
Vertices are (0, ±5) which lie on y-axis.
So the equation of hyperbola in standard form is
y2
a2
x2
b2
= 1
Now vertices are (0, ±5) ⇒ a = 5; Foci are (0, ±8) ⇒ ae = 8
Now, ae = 8 ⇒ e =
8
a
⇒ e =
8
5

We know that b = ae21 ⇒ b = 5
64
25
1
= 5
39
5
= 39
Thus required equation of parabola is
y2
(5)2
x2
(39)2
= 1 ⇒
y2
25
x2
39
= 1.
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