#include <iostream> #include <cmath> int main() { double n; std::cout << "请输入一个实数: "; std::cin >> n; if (n < 0) { std::cout << "输入的数字是负数，无法计算其平方根。" << std::endl; } else { double squareRoot = sqrt(n); std::cout << "平方根为: " << squareRoot << std::endl; } return 0; }