执笔抒情在Rt△
BCD中，CD
3
BDr
····································································································9分 tan60° ·
DC······························································································································10分 r 2 ·
23．（1）每个空格填对得1分，满分5分．
（2）解:依题意得
-··························································7分 65·
2xx
解得x 10··························································································································8分
经检验x 10是原分式方程的解 ··························································································9分
2x 20．
答:冰箱、电视机分别购买20台、10台 ····································10分 24．证明：如图1，△ABC为等边三角形
A
ABC 60°
G BC MN，BA MG
B ∴ CBM BAM 90°
C
ABM 90°- ABC 30 ················································ 1分 M 90 - ABM 60 ···················································· 2分 （图1） N 同理： N G 60 △MNG为等边三角形． ·····················
·····························
·················································3分
在Rt△ABM中，BM
ABa
sinMsin60 在Rt△
BCN中，BN
BCa a································································4分 tanNtan60 MN BM BN ························································································································
··········· 5分
（2）②：结论1成立.
证明；方法一：如图2，连接AO、BO、CO 由S△ABC S△AOB S△BOC S△AOC=作AH BC，垂足为H，
D
1
a OD OE OF ·············· 7分 2
C
则AH ACsin ACB a sin60 2
E H （图2）
