精品文档---下载后可任意编辑（1）如图 1，图 2，图 3，在中，分别以为边，向外作正三角形，正四边形，正五边形，相交于点．① 如图 1，求证：；② 探究：如图 1，；如图 2，；如图 3，．（2）如图 4，已知：是以为边向外所作正边形的一组邻边；是以为边向外所作正边形的一组邻边．的延长相交于点．① 猜想：如图 4，（用含的式子表示）；② 根据图 4 证明你的猜想．（1）①证法一：与均为等边三角形，，·················································································2 分且··············································3 分，即·····················································4 分．·················································5 分证法二：与均为等边三角形，，·················································································2 分且·················································································3 分可由绕着点按顺时针方向旋转得到·············································4 分．····················································································5 分②，，．··············································································8 分（每空 1 分）（2）①·······························································································10 分② 证法一：依题意，知和都是正边形的内角，，，，即．·········...
