7. (Sichuan Province) $\operatorname{tg} 20^{\circ} \cdot \operatorname{tg} 40^{\circ} \cdot \operatorname{tg} 60^{\circ}$ $+\operatorname{ctg} 70^{\circ}+\operatorname{tg} 40^{\circ}$ value is
7.
$$
\sqrt{3} .
$$