Tangents PA and PB are drawn to a circle x2+y2=a2 from the point (×1,y1). Equation of circumcircle of triangle PAB is

Since the circumcircle of ∆ PAB, will have the diameter joining P and the centre of the circle x^2+y^2=a^2.i.e.( 0,0)Therefore , the eq. Of the circumcircle is [ x( x-x1) + y(y-y1). ]