2.3将常数e（2.718281828）作为常量定义，然后

1、#include<iostream>

#include<iomanip>

using namespace std;

int main()

{

double e = 2.718281828;

cout << setprecision(10) << e << endl;

cout << setiosflags(ios::fixed) << setprecision(8) << e << endl;

system("pause");

}

2、#include<iostream>

#include<iomanip>

using namespace std;

int main()

{

double e = 2.718281828;

cout << setiosflags(ios::scientific) << setprecision(8) << e << endl;

system("pause");

}