Question

The eccentricity of the conic $\frac{7}{r}=2+3\cos \theta$ is

• A. $-3$
• B. $3$
• C. $\frac{3}{2}$
• D. $\frac{2}{3}$

Answer 1

Answer: (C)

$\frac{3}{2}$

$\frac{7}{r}=2+3\cos \theta$
$\Rightarrow \frac{7}{2r}=1+\frac{3}{2}\cos \theta$
Comparing with $\frac{l}{r}=1+e\cos \theta$, we get
$e=\frac{3}{2}$