分别用指数形式和小数两种格式输出

#include<iostream>
#include<iomanip>
using namespace std;
int main()
{
	const double pi = 3.14159;
	double r, c, s;
	cin >> r;
	c = 2.0*pi*r;
	s = pi * r*r;
	cout << setiosflags(ios::scientific) << c << endl;
	cout << s << endl;
	cout << setiosflags(ios::fixed) << c;
	cout << s << endl;
	system("pause");
	return 0;
}