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10-2. Parabola, Ellipse, Hyperbola
easy
Eccentricity of the ellipse $9{x^2} + 25{y^2} = 225$ is
A
$\frac{3}{5}$
B
$\frac{4}{5}$
C
$\frac{9}{{25}}$
D
$\frac{{\sqrt {34} }}{5}$
Solution
(b) The ellipse is $\frac{{{x^2}}}{{25}} + \frac{{{y^2}}}{9} = 1$
$\therefore e = \sqrt {1 – \frac{{{b^2}}}{{{a^2}}}} $
$i.e.$, $\sqrt {1 – \frac{9}{{25}}} = \frac{4}{5}$.
Standard 11
Mathematics