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10-2. Parabola, Ellipse, Hyperbola
normal
If $C$ is the centre of the ellipse $9x^2 + 16y^2$ = $144$ and $S$ is one focus. The ratio of $CS$ to major axis, is
A
$\sqrt 7 :16$
B
$\sqrt 7 :4$
C
$\sqrt 5 :\sqrt 7 $
D
$\sqrt 7 :8$
Solution
$\frac{x^{2}}{16}+\frac{y^{2}}{9}=1$
$a^{2}=16 \quad b^{2}=9$
$\mathrm{e}=\frac{\sqrt{7}}{4}$
$\mathrm{S}(\mathrm{ae}, 0)$ or $(-\mathrm{ae}, 0)$
$\mathrm{C}(0,0)$
$\mathrm{CS}=\mathrm{ae}=\sqrt{7}$
$\mathrm{CS}: 2 \mathrm{a}=\sqrt{7}: 8$
Standard 11
Mathematics