MCQ
Choose the correct answer. If e is the eccentricity of the ellipse $\frac{\text{x}^2}{\text{a}^2}+\frac{\text{y}^2}{\text{b}^2}=1(\text{a}<\text{b}),$ then:
  • A
    $b^2=a^2\left(1-e^2\right)$
  • $a^2=b^2\left(1-e^2\right)$
  • C
    $a^2=b^2\left(e^2-1\right)$
  • D
    $b^2=a^2\left(e^2-1\right)$

Answer

Correct option: B.
$a^2=b^2\left(1-e^2\right)$
  1. $a^2=b^2\left(1-e^2\right)$
Solution:
Given equation is $\frac{\text{x}^2}{\text{a}^2}+\frac{\text{y}^2}{\text{b}^2}=1(\text{a}<\text{b})$
$\therefore\text{ Eccentricity e}=\sqrt{1-\frac{\text{a}^2}{\text{b}^2}}$
$\Rightarrow\text{e}^2=1-\frac{\text{a}^2}{\text{b}^2}$
$\Rightarrow\frac{\text{a}^2}{\text{b}^2}=(1-\text{e}^2)$
$\Rightarrow\text{a}^2=\text{b}^2(1-\text{e}^2)$

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