Some of the commonly used symbols:

     \infty - Infinity

     \leq - Less then or equal

     \geq - Greater then or equal

      \partial - Partial differential

     \sum - Summa

     \prod - Product Sign

     \subset - Contained in

     \in - Element of

     \cup - Union (if you want to see big symbol, enter \bigcup

     \neq - Not equal to

     \approx - Almost equal to (asymptotic to)

     \equiv - Identical to (equivalent)

      \int - Integral

      \oint - Contour integral

word公式编辑中的转义字符