
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 $f(\alpha)= \frac {\sin (2\pi-\alpha)\cos (\pi+\alpha)\cos ( \frac {\pi}{2}+\alpha)\cos ( \frac {11\pi}{2}-\alpha)}{2\sin (3\pi +\alpha )\sin (-\pi -\alpha )\sin ( \frac {9\pi}{2}+\alpha )}$.
$(1)$ Simplify $f(\alpha)$;
$(2)$ If $\alpha=- \frac {25}{4}\pi$, find the value of $f(\alpha)$.

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