题一：打印正五角星
#include <stdio.h>
#include<graphics.h>
#include<math.h>
#define pi 3.1415926
main()
{
int driver=DETECT,mode,i;
double x,y,ang,dang;
initgraph(&driver,&mode,"");
moveto(120.00,180.00);
dang=pi+36.0/180*pi;
ang=0.0;
for(i=1;i<=5;i++)
{
setcolor(4);
x=400*cos(ang);
y=-400*sin(ang);
linerel(x,y);
ang=ang+dang;
}
getch();
closegraph();
}


题二：打印间开曲线
#include <stdio.h>
#include<graphics.h>
#include<math.h>
#define pi 3.1415926
main()
{
int driver=DETECT,mode,i,num;
double dang,x,y,r,x1,y1,ang;
printf("Please enter r and num:");
scanf("%lf%d",&r,&num);
initgraph(&driver,&mode,"");
circle(220.00,200.00,r);
dang=2*pi/360;
ang=0.0;
x1=220.00+r;y1=200.00;
for(i=0;i<=num;i++)
{
ang=ang+dang;
setcolor(4);
x=220.00+r*cos(ang)+r*ang*sin(ang);
y=200.00-r*sin(ang)+r*ang*cos(ang);
line(x1,y1,x,y);
x1=x;y1=y;
}
getch();
closegraph();
}


题三：以AB为底边画N个3至N边多边形
#include<stdio.h>
#include<graphics.h>
#include<math.h>
#define PI 3.1415926
main()
{
int driver=DETECT,mode,n,i,j,color;
double x,y,t,dang,x1,y1,ang;
initgraph(&driver,&mode,"");
x1=300.00;y1=450.00;
printf("Please enter the largest sides(>=3):");
scanf("%d",&n);
color=1;
for(i=3;i<=n;i++)
{
setcolor(color);
ang=0.0;
moveto(x1,y1);
dang=PI-PI*(i-2)/i;
for(j=1;j<=i;j++)
{
x=50*cos(ang);
y=-50*sin(ang);
linerel(x,y);
ang=ang+dang;
}
color=(color+1)%16;
}
getch();
closegraph();
}