符号(Symbol) 意义(Meaning)∞ 无穷大π 圆周率|x| 绝对值 absolute value of X∪ 并集∩ 交集= 等于 is equal to≠ 不等于 is not equal to< 小于 is less than> 大于 is greater than|| is parallel to≥ 大于等于...