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NCERT Class XI Mathematics - Conic Sections - Solutions

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Question : 28 of 71
Marks: +1, -0
x236+y216\frac{x^2}{36}+\frac{y^2}{16} = 1
Solution:  
We have been given an equation of ellipse x236+y216\frac{x^2}{36}+\frac{y^2}{16} = 1
Clearly, 36 > 16
The equation of ellipse in standard form is x2a2+y2b2\frac{x^2}{a^2}+\frac{y^2}{b^2} = 1
a2a^2 = 36 ⇒ a = 6 and b2b^2 = 16 ⇒ b = 4
We know that
c = a2b2\sqrt{a^2-b^2} ⇒ c = 3616\sqrt{36-16} = 20\sqrt{20}
∴ Coordinates of foci are (±c, 0) i.e. (± 20\sqrt{20}, 0)
Coordinates of vertices are (± a, 0) i.e. (± 6, 0).
Length of major axis = 2a = 2 × 6 = 12
Length of minor axis = 2b = 2 × 4 = 8
Eccentricity (e) = ca\frac{c}{a} = 206\frac{\sqrt{20}}{6}
Length of latus rectum = 2b2a\frac{2b^2}{a} = 2×166\frac{2 \times 16}{6} = 163\frac{16}{3}
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