Why I am seeing my opengl es like this?

Question

Seem like I'm not clearing the image correctly or something. On the other hand the view takes to much to render using the cos function. I appreciate if you can guide me to optmize the code with best practices. Thanks

And I would like to share with you this link: http://iphonedevelopment.blogspot.com/2009/05/opengl-es-from-ground-up-table-of.html

Render function inside Thumbnail3D

-(void)render
{
    Triangle3D  triangle[2];
    triangle[0].v1 = Vertex3DMake( (-width * 0.5 ) + x, (-height * 0.5 ) + y, z);
    triangle[0].v2 = Vertex3DMake( ( width * 0.5 ) + x, ( height * 0.5 ) + y, z);
    triangle[0].v3 = Vertex3DMake( (-width * 0.5 ) + x, ( height * 0.5 ) + y, z);
    triangle[1].v1 = Vertex3DMake( (-width * 0.5 ) + x, (-height * 0.5 ) + y, z);
    triangle[1].v2 = Vertex3DMake( ( width * 0.5 ) + x, ( height * 0.5 ) + y, z);
    triangle[1].v3 = Vertex3DMake( ( width * 0.5 ) + x, (-height * 0.5 ) + y, z);
    glLoadIdentity();
    glColor4f(color.red, color.green, color.blue, color.alpha);
    glVertexPointer(3, GL_FLOAT, 0, &triangle);
    glDrawArrays(GL_TRIANGLES, 0, 18);

}

drawView function inside OpenGL View

- (void)drawView:(UIView *)theView
{

    NSInteger elements = 6;
    GLfloat angle = DEGREES_TO_RADIANS( 360 / elements );
    GLfloat elementWidth = 3.0;
    //GLfloat l = ( elements * ( elementWidth + 0.2 ) ) * (elements / 300000);
    GLfloat l = elements * ( elementWidth + 0.2 ) ;
    GLfloat radius = l / (2 * M_PI);



    glLoadIdentity();
    glClearColor(1.0, 1.0, 1.0, 1.0);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glEnableClientState(GL_VERTEX_ARRAY);

    for (int columns = 0; columns < elements; columns++) 
    {
        for (int rows = 0; rows < 1; rows++) 
        {

            Thumbnail3D *thumbnail = [ [ Thumbnail3D alloc ] init ];
            thumbnail.color = Color3DMake(1.0, 0.0, 0.0, 1.0);

            thumbnail.width = 3.0;
            thumbnail.height = 2.0;

            thumbnail.x = ( ( thumbnail.width + 0.2 ) * columns ) - 3;
            //thumbnail.y = ( ( thumbnail.height + 0.2  ) * rows ) - 5;

            //thumbnail.x = sin( angle * columns ) / radius;
            thumbnail.y = ( cos( angle * columns ) / radius );
            thumbnail.z = -18;

            NSLog(@"Drawing  n%d: { radius: %f }, { angle: %f }, { x: %f }, { y: %f }", columns, radius, angle, sin( angle * columns ) / radius,cos( angle * columns ) / radius);
            NSLog(@"Drawing in: { x: %f }, { y: %f }, { z: %f }", thumbnail.x, thumbnail.y, thumbnail.z);

            [ thumbnail render ];
            [ thumbnail release ];

        }
    }

     glDisableClientState(GL_VERTEX_ARRAY);
}