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,三角形的角平分,线、中线和高,冀教版,七,年级,下,第,9,章 三角形,9.3,目标一三角形的角平分线、中线,D,C,1,2,3,4,5,B,A,6,7,8,B,答 案 呈 现,温馨,提示,:,点击,进入,讲评,习题链接,A,D,1,如,图,,AE,是,ABC,的角平分线,,AD,是,AEC,的角平分线若,BAC,80,,则,EAD,(,),A,30,B,45,C,20,D,60,2,C,【,中考,丹东】,如图,,CO,是,ABC,的角平分线,过点,B,作,BD,AC,交,CO,的延长线于点,D,,若,A,45,,,AOD,80,,则,CBD,的度数为,(,),A,100,B,110,C,125,D,135,3,B,【,点拨,】,AOD,80,,,AOC,180,AOD,180,80,100.,A,45,,,ACD,180,AOC,A,180,100,45,35.,CO,是,ABC,的角平分线,,,ACB,2,ACD,235,70.,BD,AC,,,CBD,180,ACB,180,70,110.,若,AD,是,ABC,的中线,下列结论错误的是,(,),A,AB,BC,B,BD,DC,C,AD,平分,BC,D,BC,2,DC,A,4,B,5,【,教材,P,111,习题,B,组,T,2,变式】,如图,已知,P,是,ABC,的重心,连接,AP,并延长交,BC,于点,D,,若,ABC,的面积为,20,,则,ADC,的面积为,(,),A,10,B,8,C,6,D,5,6,A,【,点拨,】,因为,P,是,ABC,的重心,所以,AD,是,ABC,的中线,所以,ADC,的面积等于,ABC,面积的一半,又因为,ABC,的面积为,20,,,所以,ADC,的面积为,10.,如,图,,D,是,ABC,中,BC,边上一点,,DE,AC,交,AB,于点,E,.,若,EDA,EAD,,试说明,AD,是,ABC,的角平分线,7,解:,DE,AC,,,EDA,CAD,.,又,EDA,EAD,,,CAD,EAD,.,AD,是,ABC,的角平分线,在,等腰三角形,ABC,中,,AB,AC,,,AC,边上的中线,BD,把,ABC,的周长分成,15,和,6,两部分,求这个三角形的腰长和底边长,8,
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