
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
Given that the terminal side of $\alpha$ passes through the point $(a, 2a)$ (where $a < 0$),
(1) Find the values of $\cos\alpha$ and $\tan\alpha$.
(2) Simplify and find the value of $$\frac {\sin(\pi-\alpha)\cos(2\pi-\alpha)\sin(-\alpha+ \frac {3\pi}{2})}{\tan(-\alpha-\pi)\sin(-\pi-\alpha)}$$.

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