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NCERT Class XI Mathematics - Conic Sections - Solutions

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Question : 38 of 71
Marks: +1, -0
Vertices (0, ±13), foci (0, ± 5)
Solution:  
Clearly, the foci (0, ±5) lie on y-axis.
∴ The equation of ellipse in standard form is x2a2+y2b2\frac{x^2}{a^2}+\frac{y^2}{b^2} = 1
Now, vertices are (0, ±13) ⇒ a = 13, foci are (0, ±5) ⇒ c = 5
Also, we know that c2c^2 = a2b2a^2 - b^2
(5)2(5)^2 = (13)2b2(13)^2 - b^2b2b^2 = 169 – 25 = 144.
Hence the required equation of ellipse is x2144+y2169\frac{x^2}{144}+\frac{y^2}{169} = 1
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