Q.

Let the circle x2+y2=4 intersect x-axis at the points A(a,0), a>0 and B(b,0).  Let P(2cosα,2sinα) 0<α<π2 and Q(2cosβ,2sinβ) be two points such that (α-β)=π2.  Then the point of intersection of AQ and BP lies on :   [2026]

1 x2+y24x4=0  
2 x2+y24y4=0  
3 x2+y24x4y-4=0  
4 x2+y24x4y=0  

Ans.

(2)

Let point of intersection R(h,k)

mBR=mBPkh+2=2sinα2cosα+2kh+2=tanα2

mAR=mAQkh-2=2sinβ2cosβ-2=sinβcosβ-1=-cotβ2

α2-β2=π4

tan(α2-β2)=tanπ4=1

tanα2-tanβ21+tanα2tanβ2=1

kh+2+h-2k1+(kh+2)(2-hk)=1

k2+h2-4k(h+2)4h+2=1

h2+k2-44k=1

x2+y2-4y-4=0