The circles k1, k2, k3 are externally tangent: k1 to k2 at point A, k2 to k3 at point B, k3 to k4 at point C, k4 to k1 at point D. The lines AB and CD intersect at the point S. A line p is drawn through point S, tangent to k4 at point F. Prove that ∣SE∣=∣SF∣. geometrycirclesequal segments