Question

An ellipse with centre at (0,0) cuts x axis at (3,0) and (-3,0). If its eccentricity is $\frac{1}{2}$ then the length of its semiminor axis is

• A.
• B.
• C.
• D. 3√3/2

Answer 1

The correct option is D

3√3/2

C(0,0), A=($\pm$3,0), a=3, e=$\frac{1}{2}$

$b^2$ = $a^2(1-e^2)$ = $9(1-\frac{1}{4})$ = $9\times \frac{3}{4}$ = $\frac{27}{4}$, b = $\frac{3\sqrt{3}}{2}$