三角形内心性质及其应用云南天然气化工厂中学徐云贵设△ＡＢＣ的边ＡＢ＝ｃ，ＢＣ＝ａ，ＣＡ＝ｂ，内心是Ｉ，外接回半径是Ｒ，内切圆半径是ｒ，∠Ａ、∠Ｂ、∠Ｃ的平分线分别交ＢＣ、ＣＡ、ＡＢ于Ｄ、Ｅ、Ｆ，则边角关系有如下的性质：证明：先证（３）．如图１，过Ｉ作... The nature and application of triangular inner core Xu Yungui, a middle school of Yunnan Natural Gas Chemical Factory, set the edge AB of △ABC, BC=a, CA=b, the inner heart is I, the outer radius is R, and the radius of inscribed circle is r, ∠A, The bisectors of ∠B and ∠C are submitted to BC, CA, and AB respectively to D, E, and F. The relationship between the corners and corners has the following properties: Proof: Proof (3). As shown in Figure 1, over I...