Points E,F are chosen on the sides CA,AB of triangle ABC. Let (K) be the circumcircle of triangle AEF. The tangents at E,F of (K) intersect at T . Prove that
(a) T is on BC if and only if BE meets CF at a point on the circle (K),
(b) EF,PQ,BC are concurrent given that BE meets FT at M,CF meets ET at N,AM and AN intersects (K) at P,Q distinct from A.Trần Quang Hùng geometryconcurrentcircumcircleTangents