(读作“派”)是一个特定的数值,约等于3.14。{"smallUrl":"https:\/\/www.wikihow.com\/images_en\/thumb\/2\/21\/Calculate-the-Radius-of-a-Circle-Step-5-Version-6.jpg\/v4-460px-Calculate-the-Radius-of-a-Circle-Step-5-Version-6.jpg","bigUrl":"https:\/\/www.wikihow.com\/images_en\/thumb\/2\/21\/Calculate-the-Radius-of-a-Circle-Step-5-Version-6.jpg\/v4-760px-Calculate-the-Radius-of-a-Circle-Step-5-Version-6.jpg","smallWidth":460,"smallHeight":345,"bigWidth":760,"bigHeight":570}2求出半径(r)。的约等数3.14来进行计算。最后得到近似结果2.39厘米。