#include <graphics.h>
#include <conio.h>
const double sin36 = 0.587785252292;
const double cos36 = 0.809016994375; 
const double tan54 = 1.376381920471; 
void s(double x,double y,double l){
    line(x,y,x+l,y);
    line(x,y,x+l*cos36,y+l*sin36);
    line(x+l,y,x+l-l*cos36,y+l*sin36);
    line(x+l-l*cos36,y+l*sin36,x+l/2,y-l/2/tan54);
    line(x+l*cos36,y+l*sin36,x+l/2,y-l/2/tan54);
}
int main(){
    double w = 800,h = 500;
    initgraph(w,h);
    s(w/2-100,h/2-100,200.0); // 正五角星 
    _getch();    
    closegraph();
    return 0;
}