做下这四道题，有偿。

用C++的方法做这几道题，要标清每个代码的题号，不需要写解释，只要把代码做出来就行。

题目1的解答代码如下：

#include<iostream>
#include<cmath>
using namespace std;

int main()
{
    int f=1, i=1;
    double x, s=1, g=1,t=1;
    cin >> x;
    for (; fabs(t)>=pow(10,-8); i++)
    {
        g *= i;
        t = (f*pow(x,i))/g;
        s += t;
        f = -f;
    }

    cout << s << endl;
    return 0;
}

第2题

#include<iostream>
#include<cmath>
using namespace std;

int main()
{
    int n = 9;
    for (int i = 1; i <= n; i++)
    {
        for (int j = 1; j <= n-i; j++)
            cout << "  ";
        for (int j = 1; j <= 2*i-1; j++)
            cout << "# ";
        cout << endl;

    }

    return 0;
}

#include<iostream>
#include<cmath>
using namespace std;

int main()
{
    int n = 15, m = 8;
    for (int i = n; i >= m; i--)
    {
        for (int j = 1; j <= n-i; j++)
            cout << " ";
        for (int j = 1; j <= i; j++)
            cout << "# ";
        cout << endl;

    }

    return 0;
}

第3题

#include<iostream>
#include<cmath>
using namespace std;

int main()
{
    cout << "*\t1\t2\t3\t4\t5\t6\t7\t8\t9" << endl;
    cout << "-----------------------------------------------------------------------------------" << endl;
    for (int i = 1; i <= 9; i++)
    {
        cout << i;
        for (int j = 1; j <= 9; j++)
            cout << "\t" << i*j;
        cout << endl;

    }

    return 0;
}

#include<iostream>
#include<cmath>
using namespace std;

int main()
{
    cout << "*\t1\t2\t3\t4\t5\t6\t7\t8\t9" << endl;
    cout << "-----------------------------------------------------------------------------------" << endl;
    for (int i = 1; i <= 9; i++)
    {
        cout << i;
        for (int j = 1; j <= i; j++)
            cout << "\t" << i*j;
        cout << endl;

    }

    return 0;
}

#include<iostream>
#include<cmath>
using namespace std;

int main()
{
    cout << "*\t1\t2\t3\t4\t5\t6\t7\t8\t9" << endl;
    cout << "-----------------------------------------------------------------------------------" << endl;
    for (int i = 1; i <= 9; i++)
    {
        cout << i;
        for (int j = 1; j < i; j++)
            cout << "\t";
        for (int j = i; j <= 9; j++)
            cout << "\t" << i*j;
        cout << endl;

    }

    return 0;
}

第4题

#include<iostream>
#include<cmath>
using namespace std;

int main()
{
    int n,a=0,b=0,c=1,t,i;
    cin >> n;
    for (i = 1; i < n; i++)
    {
        t = a + c;
        a = b;
        b = c;
        c = t;
    }
    cout << c << endl;

    return 0;
}

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