>>21 三回目。>>31は別人。
#include <iostream>
using namespace std;
int main(void)
{
double x;
cout << "Input x (-1 <= x <= 1) : ";
while( cin >> x ) {
if( !(-1.0 <= x && x <= 1.0) ) break;
double e = 0.0;
for( double n = 1.0, term = 1.0 ; term > 1e-9 || term < -1e-9 ; n += 1.0 ) {
e += term;
term *= x / n;
}
cout << e << endl;
cout << "Input x (-1 <= x <= 1) : ";
}
cout << "Good bye" << endl;
return 0;
}