This paper is a historical account of the chords theorem, for conic sections from Apollonius to Boscovich. We comment the most significant proofs and applications, focusing on Newton's solution of the Pappus four lines problem. Newton's geometrical achievements drew L'Hospital's attention to the chords theorem as a fundamental one, and led him to search for a simple and direct proof, that he finally obtained by the method of projection. Stirling gave a very elegant algebraic proof; then Boscovich succeeded in finding an almost immediate geometrical proof, and showed how to develop the elements of conic sections starting from this theorem.

这篇论文是和弦定理的历史记录，用于从 Apollonius 到 Boscovich 的圆锥曲线。我们评论了最重要的证明和应用，重点是牛顿对帕普斯四线问题的解决方案。牛顿在几何学上的成就使 L'Hospital 注意到和弦定理是一个基本定理，并促使他寻找一个简单而直接的证明，最终他通过投影的方法得到了这个证明。斯特林给出了一个非常优雅的代数证明；然后 Boscovich 成功地找到了一个几乎直接的几何证明，并展示了如何从这个定理开始发展圆锥曲线的元素。