Open GL - Dibujar circunferencia en opengl

void graficaSeno(){

float x;

glMatrixMode(GL_PROJECTION);

glLoadIdentity();

gluOrtho2D(-4,4,-1.5,1.5);

glViewport(0,altoV/2,anchoV/2,altoV/2);

glColor3ub(200,0,255);

glBegin(GL_LINES);

glVertex2f(0,-1.2);

glVertex2f(0,1.2);

glVertex2f(-3.5,0);

glVertex2f(3.5,0);

glEnd();

glColor3ub(0,0,255);

glBegin(GL_LINE_STRIP);

for(x=-PI;x<=PI;x+=0.01){

glVertex2f(x,sin(x));

}

glEnd();

}