As a kind of important energy, coal(煤炭) can _______ one day.
如图,在平行四边形ABCD中,AB=6,∠BAD的平分线与BC的延长线交于点E,与DC交于点F,且AB=3CF,DG⊥AE,垂足为G,若DG=2,则AE的边长为( )