If the angle between the straight lines joining the foci and the ends of the minor axis of the ellipse…

If the angle between the straight lines joining the foci and the ends of the minor axis of the ellipse $\frac{x^2}{a^2}+\frac{y^2}{b^2}=1$ is $90^{\circ}$, then it eccentricity is
  1. $1 / 2$
  2. $1 / 4$
  3. $1 / 3$
  4. $1 / \sqrt{2}$

Solution


Apply pythagoras theorem, in $\Delta A S_1 S_2$ $\left(S_1 A\right)^2+\left(A S_2\right)^2=\left(S_1 S_2\right)^2$ $a^2+a^2=(2 a e)^2$ $\Rightarrow \quad 2 a^2=4 a^2 e^2$ $\therefore \quad e=\frac{1}{\sqrt{2}}$

Asked in: AP EAMCET 2022 (05 Jul Shift 1)

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