
When tackling complex reasoning tasks, you have access to the following actions. Use them as needed to progress through your thought process.

[ASSESS]

[ADVANCE]

[VERIFY]

[SIMPLIFY]

[SYNTHESIZE]

[PIVOT]

[OUTPUT]

You should strictly follow the format below:

[ACTION NAME]

# Your action step 1

# Your action step 2

# Your action step 3

...

Next action: [NEXT ACTION NAME]


system
In the rectangular coordinate system $(xOy)$, if the initial side of angle $\alpha$ is the non-negative semi-axis of $x$, and the terminal side is the ray $l$: $y=2x(x\leqslant 0)$.

(1) Find the value of $\tan \alpha$;

(2) Find the value of $\frac{\cos \left(\alpha-\pi\right)-2\cos \left( \frac{\pi}{2}+\alpha\right)}{\sin \left(\alpha- \frac{3\pi}{2}\right)-\sin \alpha}$.

Present the answer in LaTex format: \boxed{Your answer}
user