? Contained in: a contains B- then b is a subset of a or equal to a.

The difference lies in the scope.

True inclusion: A is really included in the proper subset of B-if B = {1, 2}, then A={ 1} or {2} or an empty set.

Operation symbol:

Such as plus sign (+), minus sign (-), multiplication sign (× or), division sign (÷ or/), union of two sets (∩), intersection (∩), root sign (∩ ~), logarithm (log, lg, ln,

Relationship symbol:

For example, "=" is an equal sign, "≈" is an approximate sign, "≦" is an unequal sign and ">" is a greater than sign. "

"≒" is a similar symbol, "≒" is a complete equal sign, "∨" is a coordinate symbol, "is a vertical symbol," ∝ "is a direct proportion symbol (inverse ratio can be expressed by reciprocal relationship).

"∈" is a symbol, "?" Contained in the symbol "?" Does the symbol "|" in mean "divisible" (for example, a|b means "A is divisible by B", and? ||b means that R is the greatest power that A can be divisible by B), and any letter such as X and Y can represent an unknown number.