NCERT Class XI Mathematics - Conic Sections - Solutions

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Question : 35
Total: 71
16x2+y2 = 16
Solution:  
Given equation of ellipse is 16x2+y2 = 16
i.e.,
16x2
16
+
y2
16
= 1 ⇒
x2
1
+
y2
16
= 1
Clearly, 16 > 1
The equation of ellipse in standard form is
y2
a2
+
x2
b2
= 1
∴ a2 = 16 ⇒ a = 4 and b2 = 1 ⇒ b = 1
We know that c = √a2−b2 ⇒ c = √16−1 = √15
∴ Coordinates of foci are (0, ±c)
i.e. (0, ± √15)
Coordinates of vertices are (0, ± a) i.e. (0, ± 4).
Length of major axis = 2a = 2 × 4 = 8
Length of minor axis = 2b = 2 × 1 = 2
Eccentricity (e) =
c
a
=
√15
4

Length of latus rectum =
2b2
a
=
2×1
4
=
1
2
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