If the lines a1x+b1y+c1=0 and a2x+b2y+c2=0 cut the coordinates axes in concyclic points, then
Let the given lines be L1≡a1x+b1y+c1=0 and L2≡a2x+b2y+c2=0. Suppose L1 meets the coordinate axes at A and B and L2 meets at C and D. Then coordinates of A, B, C, D are
A(−c1a1,0),B(0,−c1b1)C(−c2a2,0), and D(0,−c2b2)
Since A, B, C, D are concyclic, therefore OA.OC=OD.OB
⇒(−c1a1)(−c2a2)=(c2b2)(−c1b1)⇒a1a2=b1b2