提示
⑴连接DE;∵AB=AC,AD⊥BC∴AD平分∠BAC即∠BAD=∠CAD∴∠DEF=∠DAC=∠BAC,BC切圆于D∴∠BDE=∠BAD=∠DEF∴EF∥BC
⑵连接OF,DF;由圆O 的直径AD得∠AFD=90°=∠DFC又P是DC的中点∴PF=PD∴⊿OPF≌⊿OPD(SSS)∴∠OFP=∠ODP=90°
提示
⑴连接DE;∵AB=AC,AD⊥BC∴AD平分∠BAC即∠BAD=∠CAD∴∠DEF=∠DAC=∠BAC,BC切圆于D∴∠BDE=∠BAD=∠DEF∴EF∥BC
⑵连接OF,DF;由圆O 的直径AD得∠AFD=90°=∠DFC又P是DC的中点∴PF=PD∴⊿OPF≌⊿OPD(SSS)∴∠OFP=∠ODP=90°