I am a newbie of OpenGL, here is my code desired to draw a sine wave in [0,2*pi), but there is only a line between (0,0)and(0,1), any advice is appreciated!

here is my code

//************************************************//

#include <glut.h>

#define PI 3.14159265 // _USE_MATH_DEFINES

#include <math.h>

#include <iostream>

#define SIZE 2000

void drawline(float x1, float y1, float x2, float y2);

void sinewave();

int main(int argc, char ** argv)

{ glutInit(&argc, argv);

glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA | GLUT_DEPTH);

glutInitWindowSize(400,400);

glutInitWindowPosition(200,200);

```
glutCreateWindow(" sinusoidal wave ");
glutDisplayFunc(sinewave);
glutMainLoop();
return 0;
```

}

void sinewave()

{

float x1, x2, y1, y2;

for (int i=0;i<SIZE;i++)

{

x1=i/SIZE;x2=(i+1)/SIZE;

y1=sin(x1*2*PI);

y2=sin(x2*2*PI);

drawline(x1,y1,x2,y2);

glutSwapBuffers();

}

}

void drawline(float x1, float y1, float x2, float y2)

{

glBegin(GL_LINE_STRIP); // LINE_STRIP | POINTS

glColor3f(1.0,0,0);

glVertex2f(x1,y1);

glVertex2f(x2,y2);

glEnd();

}