三角形法则是解决矢量问题的有效手段,把矢量问题在矢量三角形内进行判断和运算可使解答简捷清晰.本文从三力平衡、相对运动、速度增量和动量定理等四个方面介绍矢量三角形的用法,在研究矢量变化和求极值的过程中展示矢量三角形系图(即一簇矢量三角形)的作法和在计算中的作用 The triangle rule is an effective means to solve the vector problem. The judgment and operation of the vector problem in the vector triangle can make the solution simple and clear. This paper introduces the vector triangle from four aspects: three-force balance, relative motion, speed increment and momentum theorem. Usage, in the process of studying vector variation and seeking extremum, show the practice of vector delta system (ie a cluster of vector triangles) and its role in calculation