Enter v in sogou input method, and then you can type in each number, 1, 2, 3 ... You can see some special symbols and what you call mathematical symbols.

You can also make special symbols by typing (or using sogou): for example, you can see it by typing ch.

Also, you can see it by typing Chu.

+Enter Jia

etc

I generally support the first method.

Thank you and look forward to your adoption.