Q.

Let H be the hyperbola, whose foci are (1±2,0) and eccentricity is 2. Then the length of its latus rectum is ___________ .        [2023]

1 3  
2 52  
3 2  
4 32  

Ans.

(3)

Distance between two foci=2ae=22

⇒ae=2 ⇒ a(2)=2 (∵e=2)

⇒a=1

We know that e2=1+b2a2 ⇒ 2=1+b21

⇒b2=1 ⇒ b=1

∴ Length of latus rectum =2b2a=2(1)21=2