Forward Kinematics Problem (Rotate Robot Arm According To Input Angle)

#include<GRAPHICS.h>
#include<stdio.h>
#include<math.h>
double radian(int val)
{
  return (M_PI*val)/180;
}

void rotate(int x_c,int y_c,int a,int b,int *x_p,int *y_p,int degree)
{
   double rad=radian(degree);
   *x_p=((a-x_c)*cos(rad))-((b-y_c)*sin(rad))+x_c;
   *y_p=((a-x_c)*sin(rad))+((b-y_c)*cos(rad))+y_c;
}
int rotate_motor_logically(int motor_no,int angle,int* lx,int* ly)
{
   int a,b;
     if(motor_no==1)
     {
  rotate(lx[0],ly[0],lx[1],ly[1],&a,&b,angle);
  lx[1]=a,ly[1]=b;
  rotate(lx[0],ly[0],lx[2],ly[2],&a,&b,angle);
  lx[2]=a,ly[2]=b;
     }
     if(motor_no==2)
     {
 rotate(lx[1],ly[1],lx[2],ly[2],&a,&b,angle);
 lx[2]=a;
 ly[2]=b;
     }
     return 1;
}
int main()
{
      int lx[3],ly[3],motor_no,angle;
     /* request auto detection */
     int gdriver = DETECT, gmode;

     /* initialize graphics mode */
     initgraph(&gdriver, &gmode, "C:\\TurboC3\\BGI");

     lx[0]=getmaxx()/2;
     ly[0]=getmaxy()/2;

     lx[1]=lx[0]+110;
     ly[1]=ly[0];

     lx[2]=lx[1];
     ly[2]=ly[1]-100;

     setcolor(BLUE);
     line(lx[0],ly[0],lx[1],ly[1]);
     setcolor(RED);
     line(lx[1],ly[1],lx[2],ly[2]);

     printf("Enter motor no :\n");
     scanf("%d",&motor_no);
     printf("Enter angle :\n");
     scanf("%d",&angle);

     clrscr();
     rotate_motor_logically(motor_no,angle,lx,ly);

     setcolor(BLUE);
     line(lx[0],ly[0],lx[1],ly[1]);
     setcolor(RED);
     line(lx[1],ly[1],lx[2],ly[2]);

     getch();
 return 0;
}

Input :

Output :