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证法二：?△ABD与△ACE均为等边三角形，
····································································································· 2分 ?AD?AB，AC?AE ·
且?BAD??CAE?60 ······································································································ 3分 ············································ 4分 ?△ADC可由△ABE绕着点A按顺时针方向旋转60得到 ·
········································································································· 5分 ?△ABE≌△ADC． ·
②120，90，72． ····················································································· 8分（每空1分）
360n??????（2）① ························································································································ 10分
②证法一：依题意，知?BAD和?CAE都是正n边形的内角，AB?AD，AE?AC，
??BAD??CAE?(n?2)180n?
····································· 11分 ??BAD??DAE??CAE??DAE，即?BAE??DAC． ·
······································································································· 12分 ?△ABE≌△ADC． ·
·············· 13分 ??ABE??ADC，??ADC??ODA?180，??ABO??ODA?180
??ABO??ODA??DAB??BOC?360，??BOC??DAB?180
(n?2)180n???????BOC?180??DAB?180????360n? ·················································· 14分
证法二：同上可证 △ABE≌△AD．······································································· 12分 C ·
??ABE??ADC，如图，延长BA交CO于F，
??AFD??ABE??BOC?180，
?AFD??ADC??DAF?180 ········································· 13分
360n?????BOC??DAF?180??BAD?? ························ 14分
证法三：同上可证 △ABE≌△······································································· 12分 AD．C ·
???ABE??ADC．??BOC?180?(?ABE??ABC??ACB??ACD) ??BOC?180?(?ADC??ABC??ACB??ACD)
???ABC??ACB?180??BAC，?ADC??ACD?180??DAC
??BOC?180?(360??BAC??DAC) ···································································· 13分
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即?BOC?180??BAD??360n? ····················································································· 14分
证法四：同上可证 △ABE≌△AD．······································································· 12分 C ·
??AEB??ACD．如图，连接CE，??BEC??BOC??OCE ??AEB??AEC??BOC??ACD??ACE
············································ 13分 ??BOC??AEC??ACE． ·即?BOC?180??CAE??360n? ········································ 14分
注意：此题还有其它证法，可相应评分．
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