Both of them can be distinguished from 2, so add a point, because Z is often written as 2, and the second one is taught by our math teacher, so we use the second one uniformly.

Extended data:

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,

Relational character

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 parallel symbol, "∧" is a vertical symbol, "∧" is a proportional symbol (inverse ratio can be expressed by reciprocal relationship) and "∈" is a symbol. "contained in the symbol"? "is a containing symbol," | "means" separable "(for example, a|b? It means "A is divisible by B".

Baidu encyclopedia-mathematical symbols