c++书本题，求解了，求解

int n = 0;
    float x = 0;
    cin >> n >> x;
    float y = 0;
    int c = -1;
    for (int i = 1; i <= n ; i++)
    {
        int fenmu = 1;
        //计算阶乘
        for (int j = 1; j <= 2*i-1; j++)
        {
            fenmu *= j;
        }
        // +/-符号
        c = c * (-1);
        float fenzi = pow(x, 2 * i - 1);
        y += ((fenzi / fenmu) * c);
    }
    cout << y;