使用opengl函数写一个程序，将一个茶壶在点（100，50，0）处逆时针旋转30度，然后平移到（30，10，0）处，最后顺时针旋转50度，显示时将左上边四分之一裁减去。-To write a program using the opengl function will be a teapot at the point (100,50,0), Office of counter-clockwise rotation of 30 degrees, and then move to flat (30,10,0), Office of the final clockwise 50 degrees, the display will be left reduction to the fourth side.