(2014•湖里区模拟)如图,在Rt△ABC中,∠ABC=90°,点F为AC中点,⊙O经过点B,F,且与AC交于点D,与AB交于点E,与BC交于点G,连结BF,DE,弧EFG的长度为(1+
3
(1)求⊙O的半径;
(2)若DE∥BF,且AE=a,DF=2+