大家都很熟悉等腰三角形的性质:三线合一.鉴于很多数学定理都有逆定理,于是学生们只要看见条件中出现高线、中线、角平分线中的某两条重合,就用三线合一来说明要解决的问题,以致发生思维混乱,讲不清道理,为此我想何不干脆探讨“三线合一”的逆命题是否成立呢?为学生澄清根源,拨 Everyone is familiar with the nature of isosceles triangles: the three-wires are unity. Given that many mathematical theorems have inverse theorems, so students only need to see three conditions when they see the coincidence of some of the high, middle, and angle bisectors in the conditions. One to explain the problems to be solved, so that there is confusion in thinking, and it makes no sense. Therefore, why do I not simply discuss whether the “three-in-one” contradictory proposition is true?