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NCERT Class XI Mathematics - Conic Sections - Solutions

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Question : 35 of 71
Marks: +1, -0
16x2+y216x^2 + y^2 = 16
Solution:  
Given equation of ellipse is 16x2+y216x^2 + y^2 = 16
i.e., 16x216+y216\frac{16x^2}{16} + \frac{y^2}{16} = 1 ⇒ x21+y216\frac{x^2}{1} + \frac{y^2}{16} = 1
Clearly, 16 > 1
The equation of ellipse in standard form is y2a2+x2b2\frac{y^2}{a^2} + \frac{x^2}{b^2} = 1
a2a^2 = 16 ⇒ a = 4 and b2b^2 = 1 ⇒ b = 1
We know that c = a2b2\sqrt{a^2 - b^2} ⇒ c = 161\sqrt{16 - 1} = 15\sqrt{15}
∴ Coordinates of foci are (0, ±c)
i.e. (0, ± 15\sqrt{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) = ca\frac{c}{a} = 154\frac{\sqrt{15}}{4}
Length of latus rectum = 2b2a\frac{2b^2}{a} = 2×14\frac{2 \times 1}{4} = 12\frac{1}{2}
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