执笔抒情S△ABC
11BC·AH a· 222
11 a
OD OE OF a
22 OD OE OF
··································································································8分 ·方法二：如图3，过点O作GH∥BC，分别交AB、AC于点G、H，过点
H作HM⊥BC于点M，
DGO B 60°， OHF C 60° △AGH是等边三角形 GH AH ···································································· 6分 OE⊥BC OE∥HM
四边形OEMH是矩形 HM OE······································································· 7分
在Rt△
ODG中，OD OG·sin DGO OG·sin60
A
在Rt△
OFH中，OF OH·sin OHF OH·sin60
在Rt△
HMC中，HM HC·sinC HC·
sin60
HC O
OD OE OF OD HM OF
HC 222
E M （图3）
（2）②:结论2成立．
Aa ···························8分
GH HC 222
E
E
证明：方法一：如图４，过顶点A、B、C依次作边
AB、B、CCA△MNG，NG为等边
的垂线围成由（1）得△M
三角形且MN ··············································· 9分
G
D MN于D ,OE NG于NG于点过点O分别作OD MGE ，OF于点F
由结论1得：
N
（图4）
