Internal bisector ∠A of △ABC meets side BC at D.A line drawn through D perpendicular to AD intersects the side AC at E & side AB at F. If a, b, c represent sides of △ABC, then
(a) AE is the HM of b & c
(b) AD = \(\frac{2bc}{b+c}\) cos\(\frac A2\)
(c) EF = \(\frac{4bc}{b+c}\) sin\(\frac A2\)
(d) △AEF is isosceles
