
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 $f(x)= \frac {\cos (x- \frac {\pi}{2})}{\sin ( \frac {7\pi}{2}+x)}\cdot\cos (\pi-x)$．  
$(1)$ Simplify the expression of $f(x)$;  
$(2)$ If $f(\alpha)=- \frac {5}{13}$, find the values of $\cos \alpha$ and $\tan \alpha$．

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