已知,如图在梯形ABCD中,AB∥DC,AD=BC,延长BA到E,使AE=CD,连结DE.(1)若CD:AB=3:5,过点B作BF⊥DE于F,且BF平分∠ABC,求△BEF与四边形BCDF的面积之比;(2)在(1)的条件下:求cos∠FDB的值.

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