Motivated by recent questions about the extension of Courant’s nodal domain theorem, we revisit a theorem published by C. Sturm in 1836, which deals with zeros of linear combination of eigenfunctions of Sturm–Liouville problems. Although well known in the nineteenth century, this theorem seems to have been ignored or forgotten by some of the specialists in spectral theory since the second half of the twentieth-century. Although not specialists in History of Sciences, we have tried to put this theorem into the context of nineteenth century mathematics.

中文翻译：

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关于本征函数线性组合的零点的Sturm定理

受有关Courant节点域定理扩展的最新问题的推动，我们回顾了C. Sturm在1836年发布的一个定理，该定理涉及Sturm-Liouville问题的本征函数线性组合的零。尽管在19世纪广为人知，但自20世纪下半叶以来，这一定理似乎已被频谱理论的一些专家所忽略或遗忘。尽管不是科学史专家，我们还是试图将这个定理纳入19世纪数学的范畴。