打印正弦曲线
   整型数组sin2[100]存放正弦函数的值，假设屏幕共有80列，将区别[-PI,PI]分为80等份
   #include "stdio.h"
   #include "math.h"
   const double PI=3.14159265;
   main()
   {
      int j,k,sin2[100];
      double x,t;
      t=__________;
      for (j=0,x=-PI;x<PI;x=x+t,j++)
      sin2[j]=floor(_________________);
      printf("\n");
      for (k=11;k>=-9;k--)
     {
       for (j=0;j<=80;j++)
         if (j==40)
           putchar('|');
         else
           if(____________)
           putchar('*');
         else
           if (________)
           putchar(' ');
         else
           putchar('-');
         printf("\n");
      }
  }