三质点质心的一个充要条件

A sufficient and necessary condition for center of tri-particle

从三角形的一个性质中得出三质点质心满足的一个向量表达式,并得到两个有实用价值的推论,同时对上一性质给出两个简洁的证明。

From a property of the triangle a vector expression is deduced with two practical corollaries. Here two proofs are presented.