主题：用for循环如何编写

for(int i=1;i<=n;i++)

{

    y=y+sin(i/n)*x[i];                 //x数组在前面自行先定义好

}

int[] x = new int[5];
            double y = 0;
            double n = 5;

            for (int j = 1; j <= n;j++ )
            {
                x[j - 1] = j;
            }
                for (int i = 1; i <= n; i++)
                {

                    y = y + (i/n)* x[i-1];                                

                }
                Console.WriteLine(y);

你输出y看下就对了。