def METHOD_NAME(*args):
    prev.delete("all")
    try:
        count = vars['count'].get()
        th0 = vars['th0'].get()
        inc = vars['inc'].get()
    except ValueError: return
    for i in range(count):
        th = (th0 + i * inc) * math.pi / 180
        x = 100 + 75 * math.cos(th)
        y = 100 - 75 * math.sin(th)
        prev.create_oval((x-4,y-4,x+4,y+4), fill='black')