The symbol of belonging is ∈.

As for the ones that are not symbols, I suggest you go/download a "mathematical tool" software, which is specially used to insert mathematical symbols (roots, fractions, equations) and function images in Word documents. It has the advantages of fast input speed and convenient use. If you can use it skillfully, the speed of inputting mathematical formulas will be several times or even dozens of times that of using the formula editor! The function image inserted with Math tool also has the effect of zooming in and out, without distortion and sawtooth! It is very convenient to use, which can greatly save your time and improve work efficiency. Give it a try!