https://s0.wp.com/latex.php?latex=%28U_1+%5Ctimes+V_1%29+%5Ctimes+%28U_2+%5Ctimes+V_2%29+%3D+%28U_1+%5Ccap+U_2%29+%5Ctimes+%28V_1+%5Ccap+V_2%29&bg=%23ffffff&fg=%23111111&s=0