看看下面这个怎么样:
#include<graphics.h>
#include<math.h>
main()
{
int gd=DETECT;
int gm,i,a[6],b[6];
initgraph(&gd,&gm,"");
setcolor(2);
circle(320,240,150);
for(i=0;i<=5;i++)
{a[i]=320+150*sin(3.1415927*0.8*i);
b[i]=240-150*cos(3.1415927*0.8*i);
}
setcolor(4);
for(i=0;i<=4;i++)
line(a[i],b[i],a[i+1],b[i+1]);
}