2. "∴" means: so.

3. "∷" means: equal to, in proportion.

This is a special mathematical term.

"∫" and "∴" were first used by Swiss mathematician John Rehn. In a math book "Teusche Algebra" published by 1659, he used "∴" and "⊙" to mean "so".

Extended data

Mathematical symbols:

1. Perhaps China's ancient calculation and compilation is one of the earliest symbols used in the world, which originated from divination in Shang Dynasty.

2. Most mathematical symbols we use today were invented after16th century. Before that, mathematics was written in words, which was a hard procedure that would limit the development of mathematics.

Today's symbols make mathematics easier for people to operate, but beginners are often afraid of it. It is extremely compressed, and a small number of symbols contain a lot of information. Like music notation, today's mathematical symbols have clear grammar and information coding, so it is difficult to write them in other ways.

Baidu Encyclopedia: Mathematics