Q.

Consider a branch of the hyperbola x2-2y2-22x-42y-6=0 with vertex at the point A. Let B be one of the end points of its latus rectum. If C is the focus of the hyperbola nearest to the point A, then the area of the triangle ABC is              [2008]

1 1-23  
2 32-1  
3 1+23  
4 32+1  

Ans.

(2)

Given hyperbola is

x2-2y2-22x-42y-6=0

(x2-22x+2)-2(y2+22y+2)=6+2-4

(x-2)2-2(y+2)2=4

(x-2)222-(y+2)2(2)2=1

 a=2, b=2e=1+24=32

Clearly ABC is a right triangle.

 Area(ABC)=12×AC×BC

=12(ae-a)×b2a

=12(e-1)×b2

=12(32-1)×2

=32-1