Making a clock using c graphics

Following is the program to make a clock.
        
#include<graphics.h>
#include<stdio.h>
#include<conio.h>
#include<math.h>
#include<dos.h>

// Calculates new co-ordinates of a figure after 
// rotating it at an angle about a point (cx,cy)
void rotate( int figure[], int edges, double angle, int cx, int cy )
{
double x, y;
angle = -1 * (angle*3.14/180);
double cos_a = cos(angle);
double sin_a = sin(angle);

for(int i=0; i < edges; i++)
{
x = figure[2*i] - cx;
y = figure[2*i+1] - cy;
figure[2*i] = floor( (x * cos_a) - (y * sin_a) + cx + 0.5 );
figure[2*i+1] = floor( (x * sin_a)+(y * cos_a) + cy + 0.5 );
}
}

void drawClock(int,int,int);

void main()
{
int second_hand[4],minute_hand[4], hour_hand[4], edges = 2 ;
double angle;
int cx=300, cy=200;
int gd = DETECT, gm;
initgraph( &gd, &gm, "" );
int max_y = getmaxy();
clrscr();
cleardevice();

angle = -6;

// Set the initial position of the second, minute and the hour hands.

second_hand[0] = cx ;
second_hand[1] = max_y - cy;
second_hand[2] = cx;
second_hand[3] = max_y - 320;

hour_hand[0] = cx;
hour_hand[1] = max_y - cy;
hour_hand[2] = cx + 90;
hour_hand[3] = max_y - 200;

minute_hand[0] = cx;
minute_hand[1] = max_y - cy;
minute_hand[2] = cx;
minute_hand[3] = max_y - 310;

cleardevice();
setbkcolor(WHITE);

// Draw the clock
drawClock(cx,max_y - cy,150);
setlinestyle(SOLID_FILL,0,1);

// Draw the minute and the hour hand
drawpoly(2,minute_hand);
drawpoly(2,hour_hand);

int i=0;
while(!kbhit()) {
setcolor(RED);
drawpoly(2,second_hand);
setcolor(GREEN);
drawpoly(2,minute_hand);
setcolor(BLUE);
drawpoly(2,hour_hand);
delay(1000);   // set delay(10) to tick the clock fast
setcolor(15);
drawpoly(2,second_hand);
rotate(second_hand,edges,angle,cx,max_y - cy);
i++;

// Reset the second hand and move the minute hand 
// when the second hand has moved 60 times.
if(i%60 == 0) {
second_hand[0] = cx ;
second_hand[1] = max_y - cy;
second_hand[2] = cx;
second_hand[3] = max_y - 320;
drawpoly(2,minute_hand);
rotate(minute_hand,edges,angle,cx,max_y - cy);
}

// Move the minute hand 
// when the second hand has moved 720 (60*12) times.
if(i%720 == 0) {
i = 0;
drawpoly(2,hour_hand);
rotate(hour_hand,edges,angle,cx,max_y - cy);
}

}

getch();
}

// Function to draw the clock 
void drawClock(int cx, int cy, int r) {
setcolor(GREEN);
setlinestyle(SOLID_FILL,0,3);
circle(cx,cy,r);

int max_y = getmaxy();
int center[2] = {cx, max_y - 340};

for(int i=0; i<60; i++) {
if(i%5 == 0) {
circle(center[0],center[1],2);
} else {
circle(center[0],center[1],1);
}
rotate(center,1,-6,cx,cy);
}
}

Output: