Same as $\displaystyle \tan 90°$

$\tan(x)=\frac{\sin(x)}{\cos(x)}$ $\tan270°=\frac{\sin 270° }{\cos 270°}$ $\tan270°=\boxed{\large{\frac{-1}{0}}}$

Sorry, I can't evaluate $\displaystyle \frac{-1}{0}$ .

tan(270)=tan(360-90)= -tan90= undefined