Rotation of Fan in C

#include<graphics.h>
#include<stdio.h>
#include<stdlib.h>
#include<conio.h>
#include<dos.h>
#include<time.h>
#include<process.h>
#include<math.h>
void user();
float s1 = 0.0, s2 = 120.0, s3 = 240.0;
int midx, midy;
void main() {
    int gdriver = DETECT, gmode, errorcode;
    initgraph( & gdriver, & gmode, "C:/TC/BGI");
    errorcode = graphresult();
    if (errorcode != grOk) {
        printf("Graphics error: %s\n", grapherrormsg(errorcode));
        printf("Press any key to halt:");
        getch();
        exit(1);
    }
    midx = getmaxx() / 2;
    midy = getmaxy() / 2;
    loop:
        cleardevice();
    circle(midx, midy, 5);
    setcolor(10);
    line(midx, midy, (midx + 100 * cos(s1 * 3.14 / 180)), (midy - 95 * sin(s1 * 3.14 / 180)));
    line(midx, midy, (midx + 100 * cos(s2 * 3.14 / 180)), (midy - 95 * sin(s2 * 3.14 / 180)));
    line(midx, midy, (midx + 100 * cos(s3 * 3.14 / 180)), (midy - 95 * sin(s3 * 3.14 / 180)));
    if (!kbhit()) //check for keystroke
    {
        s1 += 10;
        s2 += 10;
        s3 += 10;
        delay(25);
        goto loop;
    } else //when key press
    {
        getch();
        exit(0);
    }
    getch();
    closegraph();
}