1.

If angle between asymptotes of hyperbola x2/a2 - y2/b2 = 1 is 120° and product of perpendiculars drown from foci upon its any tangent is 9, then locus of point of intersection of perpendicular tangents of the hyperbola can be(a)  x2 + y2 = 18(b)  x2 + y2 = 6(c)  x2 + y2 = 9(d)  x2 + y2 = 3

Answer»

Correct option  (a) x+ y2 = 18

Explanation:

2tan–1 b/a =  60°

b/a = 1/√3

b2 = 9

∴ a2 = 27

Required locus is director circle i.e

x+ y2  = 27 – 9

x+ y2 = 18

If b/a = tan 60° = √3

a2 = 3

Then equation of director circle is x+ y2  = 3 - 9 = -6 which is not possible.



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