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10-2. Parabola, Ellipse, Hyperbola
easy
If the length of the major axis of an ellipse is three times the length of its minor axis, then its eccentricity is
A
$\frac{1}{3}$
B
$\frac{1}{{\sqrt 3 }}$
C
$\frac{1}{{\sqrt 2 }}$
D
$\frac{{2\sqrt 2 }}{3}$
Solution
(d) Major axis = $3$ (Minor axis)
==> $2a = 3(2b)$
==> ${a^2} = 9{b^2} = 9{a^2}(1 – {e^2})$
==> $e = \frac{{2\sqrt 2 }}{3}$.
Standard 11
Mathematics