# Context Free Grammar proof

For example looking at the following Context Free Grammars

$G_1&space;=&space;(V_1,&space;T_1,&space;S_1,&space;P_1)$
and
$G_2&space;=&space;(V_2,&space;T_2,&space;S_2,&space;P_2)$

How do I use that to show that the language $L&space;=&space;L_1&space;\cup&space;L_2$
is also Context Free?

L1 and L2 are the Context Free Languages produced by G1 and G2 respectively