![](https://static.youtibao.com/asksite/comm/h5/images/m_q_title.png)
[单选题]
如图,AD是△ABC的角平分线,DE⊥AB,DF⊥AC,垂足分别为点E、点F,连接EF与AD相交于点O,下列结论一定成立的有()个 ①DE=DF②AD垂直平分EF③EF垂直平分AD④AD平分角EDF⑤AE=AF⑥△ADE和△ADF关于AD轴对称
A.2
B.3
C.4
D.5
![](https://static.youtibao.com/asksite/comm/h5/images/m_q_a.png)
D、5
![](https://static.youtibao.com/asksite/comm/h5/images/solist_ts.png)
A.2
B.3
C.4
D.5
D、5
A.30°
B.40°
C.50°
D.60°
A.全等三角形的性质
B.全等三角形的判定(SSS;SAS,ASA;AAS,HL)
C.角平分线的性质
D.角平分线的判定