JY的答案 俊奕 · 发布于 2025-10-04 · 浏览 299 回复 0 include <bits/stdc++.h> using namespace std; int main() { double a, b, c, d; cin >> a; b = a * 2; c = b * 3.1415926; d = 3.1415926 * a * a; printf("%.4lf %.4lf %.4lf", b, c, d); }