Нужна помощь с С++

#include <iostream>
#include <iomanip>
using namespace std;
int main() {
double y;
cout << fixed;
for (int n = 0; n < 100; ++n) {
auto x = n / 10.;
if (x <= 5) y = -1;
else if (x > 8) y = sin(x);
else y = x * x;
cout << "f(" << setprecision(1) << x << ") = ";
if (x <= 5) cout << setprecision(0);
else if (x > 8) cout << setprecision(15);
else cout << setprecision(2);
cout << y << '\n';
}
system("pause > nul");
}

#include iostream
#include cmath
#include iomanip

using namespace std;

int main() {
    double x, y;
    x = 0;
    while(x <= 10)
    {
        cout << "x = " << setw(3) << x << ", ";
        if (x <=5)
            y = -1;
        else if (5 < x && x <= 8)
            y = x * x;
        else
            y = sin(x);
        cout << "y = " << y << endl;
        x = x + 0.1;
    }
    return 0;
}

В массиве Y хранятся значения

#include math.h

int main()
double Y[101]; double x=0.0; double delta= 0.1;
int index= 0;

while (x!=5.1) { Y[index]= -1; x+= delta; index++; }
while (x!=8.1) { Y[index]= x*x; x+= delta; index++; }
while (x!=10.1) { Y[index]= sin(x); x+= delta; index++; }
return 0;
}