我们知道 ,三角形有以下一个性质 :图 1如图 1,设过△ ABC的重心 G的任一直线 l与△ABC的三边分别相交于 x,y,z三点 ,则有 1GX+1GY+1GZ=0 (这里 GX等指有向线段的数量 ,下同 ) .经研究 ,笔者发现三棱锥的重心也有类似的性质 :如图 2 ,设过三棱锥 P- ABC的重心 G任图 2一直线 l We know that the triangle has one of the following properties: Fig.1 As shown in Fig.1, if any line of the center of gravity G of △ ABC is set to intersect with the three sides of △ABC at the three points of x,y,z, there is 1GX+1GY+ 1GZ = 0 (here GX refers to the number of directed segments, the same below). After research, the author found that the center of gravity of the triangular pyramid also has similar properties: as shown in Figure 2, the center of gravity of the P-ABC is set as Figure 2 Line l