人教版四年级数学下册三角形的内角和--ppt课件

,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,LOGO,COMPANY LOGOTYPE INSERT,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,LOGO,COMPANY LOGOTYPE INSERT,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,LOGO,COMPANY LOGOTYPE INSERT,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,LOGO,COMPANY LOGOTYPE INSERT,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,*,*,*,*,*,*,*,*,*,*,*,*,三角形的内角和,三角形的内角和,一、情境引入,我的内角和也不比你们小。,我有一个钝角,我的内角和是最大的,!,我长得又高又壮,我的内角和才是最大的,!,o,一、情境引入我的内角和也不比你们小。我有一个钝角,我的内角和,1,2,3,1,、,2,、,3,都是这个三角形的内角。,内角和：,1+2+3,1231、2、3都是这个三角形的内角。内角和：1+,一、情境引入,我的内角和也不比你们小。,我有一个钝角,我的内角和是最大的,!,我长得又高又壮,我的内角和才是最大的,!,o,一、情境引入我的内角和也不比你们小。我有一个钝角,我的内角和,二、探究新知,30,60,90,45,90,45,你知道三角尺内角的,度数分别是多少吗？,90+45+45=180,90+30+60=180,每个三角尺的内角度数之和都是,180,。,猜想：是不是所有的三角形的内角和都是,180,？,二、探究新知 306090459045你知道三,二、探究新知,锐角三角形,钝角三角形,直角三角形,50+80+50=180,40+110+30=180,90+68+22=180,小结：通过测量的方法，可以发现三角形的内角和是,180,。,量,二、探究新知锐角三角形钝角三角形直角三角形50+80+5,剪,平角：,180,0,二、探究新知,平角：,180,0,平角：,180,0,锐角三角形,钝角三角形,直角三角形,小结：通过剪拼的方法，三角形的,三个内角正好拼成一个平角,，因为平角是,180,，所以三角形的内角和是,180,。,剪平角：1800二、探究新知平角：1800平角：1800锐角,二、探究新知,3,1,2,2,1,3,平角,=180,0,折,3,1,2,2,1,3,平角,=180,0,1,1,2,3,2,3,平角,=180,0,小结：通过折叠的方法，三角形的,三个内角折到一起