If the chord of contact of tangents from a point P(h,k) to the circle x² + y² = a² touches the circle x² + (y-a)² = a² , then locus of P is

Equation of chord of contact from p(h,k) to x²+ y² = a² is xh + yk = a²  this line touches (x)² + (y-a)² = a² substituting x= (a²-yk)/h from the first equation, we get a quadratic in y.The line touches the second circle in only one point, so discriminant should be equal to zero. We get,      h²+ 2a²k² + 2ak -a²= 0 , therefore the required locus is x² +2a²y² +2ay -a²=0