In Euclid's Elements of Geometry published by Cambridge University 1827, ∫ means "because" and ∴ means "so" respectively. This usage has become more and more popular and has been used ever since.

The common scene of these two symbols in extended materials is in the process of mathematical calculation, which needs to be solved by the known conditions given by the topic.

According to the meaning of the topic, the known conditions that can be obtained are generally deduced by adding the "∵" symbol and the known conditions when necessary.

If the related relations, logics and figures can be deduced from the known conditions, the symbol "∴" is used and the corresponding conclusion is added as a summary.