摘要：
+ plus 加号；正号 - minus 减号；负号 ± plus or minus 正负号 × is multiplied by 乘号 ÷ is divided by 除号 ＝ is equal to 等于号 ≠ is not equal to 不等于号 ≡ is equivalent to 全等于号 ≌ is equal to or approximately equal to 等于或约等于号 ≈ is approximately equal to 约等于号 ＜ is less than 小于号 ＞ is more than 大于号 ≮ is not less 阅读全文