江苏省扬州市竹西中学2016-2017学年八年级上月考数学试卷（10月份）含答案解析  
5．下列图形：①角；②直角三角形；③等边三角形；④线段；⑤等腰三角形．其中一定是轴对称图形的有（　　）                                                                           
A．2个        B．3个        C．4个         D．5个
【考点】轴对称图形．                                                                        
【分析】根据轴对称图形的概念对各小题分析判断后即可得解．                     
【解答】解：①角是轴对称图形；                                                          
②直角三角形不一定是轴对称图形；                                                       
③等边三角形是轴对称图形；                                                                 
④线段是轴对称图形；                                                                            
⑤等腰三角形是轴对称图形；                                                                 
综上所述，一定是轴对称图形的有①③④⑤共4个．                                  
故选：C．                                                                                          
【点评】本题考查了轴对称图形的概念．轴对称图形的关键是寻找对称轴，图形两部分折叠后可重合．                                                                                                                      
6．到三角形三条边的距离都相等的点是这个三角形的（　　）                       
A．三条中线的交点     B．三条高的交点                                            
C．三条边的垂直平分线的交点     D．三条角平分线的交点           
【考点】角平分线的性质．                                                                      
【分析】因为角的平分线上的点到角的两边的距离相等，所以到三角形的三边的距离相等的点是三条角平分线的交点．                                                                            
【解答】解：                                                                                      
∵角的平分线上的点到角的两边的距离相等，                                          
∴到三角形的三边的距离相等的点是三条角平分线的交点．                            
故选：D．                                                                                          
【点评】该题考查的是角平分线的性质，因为角的平分线上的点到角的两边的距离相等，所以到三角形的三边的距离相等的点是三条角平分线的交点，易错选项为C．