从三角形一个顶点引出的关于角平分线对称的射线 (或其相应线段 )叫做等角线 ,在三角形内 (外 )的称内 (外 )等角线 .本文将给出三角形等角线的一个新性质 .即定理　设 AP、AQ为△ ABC( ABAC)的等角线 ,AD为△ ABC的∠ BAC的内角平分线 ,则1CD- 1BD=1QD 1PD,图 1式中右端“ ” The ray (or its corresponding line segment) symmetric about the bisector drawn from a vertex of the triangle is called the isoline, and the inside (outside) isometric inside the triangle (outer). This article will give a triangle isometric The new property: the theorem sets AP and AQ as the isometric lines of △ ABC (ABAC), AD is the △ ABC of the internal angle bisector of ∠ BAC, then 1CD-1BD=1QD 1PD, and the right end of Figure 1