418. Calculate $\operatorname{tg}\left(-300^{\circ}\right)$.
Solution. The function $y=\tan x$ is odd, so $\tan\left(-300^{\circ}\right)=$ $=-\tan 300^{\circ}$. Since $300^{\circ}=270^{\circ}+30^{\circ}$ and the angle $300^{\circ}$ ends in the IV quadrant, then

$$
\tan\left(-300^{\circ}\right)=-\tan 300^{\circ}=-\tan\left(270^{\circ}+30^{\circ}\right)=\cot 30^{\circ}=\sqrt{3} .
$$