Let B be the centre of the circle x^2+y^2-2x+4y+1=0. Let the tangents at two points P and Q on the circle intersect at the point A(3,1). Then 8(…
JEE Main 2021 — Mathematics Coordinate Geometry
2021integermedium
Let B be the centre of the circle x2+y2−2x+4y+1=0. Let the tangents at two points P and Q on the circle intersect at the point A(3,1). Then 8(areaΔBPQareaΔAPQ) is equal to .
Official previous-year question
Held on 31 Aug 2021 · Verified 6 Jul 2026.
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Solution
Given, centre of circle x2+y2−2x+4y+1=0.....(i)
Points B(1,-2)&A(3,1)
For point P,y=−2
Putting value of y in equation (i)
x2+(−2)2−2x+4×(−2)+1=0
x2−2x−3=0
(x−3)(x+1)=0
x=−1 (not possible)
x=3
Point P(3,−2)
AP=(3−3)2+(−2−1)2
AP=3=AQ
r=(1)2+(−2)2−1
r=1+4−1
r=2
tanθ=23
Area(ΔBPQ)Area(ΔAPQ)=RBAR
=2cosθ3sinθ=49
8(Area(ΔBPQ)Area(ΔAPQ))=18
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