Case I..if the angle b/w the tangents is 90°..then the locus of that point will be x2 + y2 = 2a2 ..if the equation of the circle is x2 + y2 = a2
Case II : If the angle b/w the tangents is 2θ ..
take the centre of the circle at origin and radius is r..
then the distance of the point from where the tangent is drawn will be r/sinθ ..by trigonometry..
so the locus will be x2 + y2 = r2 / sin2θ..