If a focal chord of the ellipse $\frac{x^2}{25}+\frac{y^2}{16}=1$ meets its minor axis at the point $(0,3)$,…

If a focal chord of the ellipse $\frac{x^2}{25}+\frac{y^2}{16}=1$ meets its minor axis at the point $(0,3)$, then the perpendicular distance from the centre of the ellipse to this focal chord is
  1. $5$
  2. $\frac{2}{\sqrt{5}}$
  3. $1$
  4. $\frac{3}{\sqrt{2}}$

Solution


Let $A=(0,3)$ Given the ellipse, $\frac{x^2}{25}+\frac{y^2}{16}=1$ So focus of the ellipse $F=\left(\sqrt{5^2-4^2}, 0\right)$ $\Rightarrow \mathrm{F}=(3,0), \mathrm{P}\left(\frac{0+3}{2}, \frac{3+0}{2}\right)=\left(\frac{3}{2}, \frac{3}{2}\right)$ So required distance $=\sqrt{\left(\frac{3}{2}\right)^2+\left(\frac{3}{2}\right)^2}=\sqrt{\frac{18}{4}}$ $=\sqrt{\frac{9}{2}}=\frac{3}{\sqrt{2}}$

Asked in: AP EAMCET 2023 (16 May Shift 2)

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