Đáp án + Giải thích các bước giải:

$\begin{array}{l} & \tan \bigg(x - \dfrac{5\pi}{2}\bigg)
\\ &= \dfrac{\sin \big(x - \frac{5\pi}{2}\big)}{\cos \big(x - \frac{5\pi}{2}\big)}
\\ &= \dfrac{\sin x \cos \frac{5\pi}{2} - \cos x \sin \frac{5\pi}{2}}{\cos x \cos \frac{5\pi}{2} + \sin x \sin \frac{5\pi}{2}}
\\ &= \dfrac{0 - \cos x}{0 + \sin x}
\\ &= \dfrac{-\cos x}{\sin x}
\\ &= -\cot x
\\ &= -\dfrac{1}{\tan x}
\\ &= -\dfrac{1}{2} \end{array}$

$\Rightarrow$ Trả lời: $\begin{array}{|c|c|c|}\hline \text{$-$}&\text{$0$}&\text{$,$}&\text{$5$}\\\hline\end{array}$