Question

已知：如图,在△ABC中,AB=AC,AD平分∠BAC交BC于点D,BE平分∠ABC交AD于点E,F是边AB上一点,以B

Answer 1

AB = AC ,AD平分∠BAC

cosC = 1/3

cosB = cosC

cosB = (BC/2)/AB = R/(AB - R) = 1/3

R = 3/2

R = (2/3)(BC/2) = 4/3