常用算术平方根：

√0 = 0（表示根号0等于0，下同）

√1 = 1

√2 = 1.4142135623731

√3 = 1.73205080756888

√4 = 2

√5 = 2.23606797749979

√6 = 2.44948974278318

√7 = 2.64575131106459

√8 = 2.82842712474619

√9 = 3

√10 = 3.16227766016838

√11 = 3.3166247903554

√12 = 3.46410161513775

√13 = 3.60555127546399

√14 = 3.74165738677394

√15 = 3.87298334620742