欧拉公式的推理和最终表达式：https://dayi.jd100.com/question/2051787/
欧拉公式应用：题目：https://cn.vjudge.net/contest/242365#problem/H
代码链接 ：https://blog.csdn.net/creat2012/article/details/40736115
ac代码：
#include<iostream>
#include<queue>
# include<bits/stdc++.h>
using namespace std;
int main(){
double p,q, r, n, m, l;
while(cin>>n>>m>>p>>l>>q>>r){
double rr = r * r, mm = m * m, nn = n * n;
double pp = p * p, qq = q * q, ll = l * l;
double x1 = (pp + qq - nn) / 2.0, x2 = (pp + rr - mm) / 2.0, x3 = (qq + rr - ll) / 2.0;
double v = pp * (qq * rr - x3 * x3) - x1 * (x1 * rr - x2 * x3) + x2 * (x1 * x3 - qq * x2);
cout<<fixed<<setprecision(4)<<sqrt(v) / 6.0<<endl;
}
return 0;
}