顯然,AXDY四點(diǎn)共圓,結(jié)合AXDY共圓與XY∥FP得,∠XAD=∠XYD=∠FPD,于是AFDP共圓,由FD∥AC知DF丄DP,所以AF丄AP,DE丄AP,故E為角ADP的垂心,所以Ep丄AD