Question
If a variable tangent of the circle x2+y2=1 intersect the ellipse x2+2y2=4 at P and Q then the locus of the points of intersection of the tangents at P and Q is
Answer: Option D
:
D
x2+y2=1; x2+2y2=4
Let R(x1,y1) is point of intersection of tangents drawn at P,Q to ellipse ⇒ PQ is chord of contact of R(x1,y1)
⇒xx1+2yy1−4=0
This touches circle ⇒r2(l2+m2)=n2⇒1(x21+4y21)=16⇒x2+4y2=16isellipsewitheccentricitye=√32andlengthoflatusrectumLL1=2
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D
x2+y2=1; x2+2y2=4
Let R(x1,y1) is point of intersection of tangents drawn at P,Q to ellipse ⇒ PQ is chord of contact of R(x1,y1)
⇒xx1+2yy1−4=0
This touches circle ⇒r2(l2+m2)=n2⇒1(x21+4y21)=16⇒x2+4y2=16isellipsewitheccentricitye=√32andlengthoflatusrectumLL1=2
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