如图,在直角梯形ABCD中,AD∥BC,∠ABC=90°,BD⊥DC,BD=DC,CE平分∠BCD,交AB于点E,交BD于点H,EN∥DC交BD于点N.下列结论:
①BH=DH;
②
;
③
.
其中正确的是( )

- A.①②③
- B.②③
- C.只有②
- D.只有③
答案
正确答案:B

过H做HG⊥BC于点G,CE平分∠BCD,BD⊥CD,
△CGH≌△CDH,∴DH=GH, CG=CD
∵在△BGH中,
∴BH>GH,
∴BH>DH
∴①不对
∵△GCH∽△BCE
∴CH/EH=CG/BG
CG=CD
∠CBD=45°,∴△BGH为等腰直角三角形,BG=GH=DH,BG/BH=1:;
BG:CG=BG:BD=BG:(BH+DH)=BG:(BH+BG)=1:(1+)=EH:CH,
∴②正确,CH=(1+)EH
③△ENH和△EBH同高,高都等于E到BH的距离,底不同。S△ENH:S△EBH=NH:BH
BG:CG=1:(1+),CG:BC=1:
,GH:BE=1:
,∴BH=BE=DN,
BH=NH+BN=NH+HD
NH:BH=NH:DN,
NH:DH=EH:CH
∴NH:DN=EH:CE
③正确

略
