
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 $α$ is an angle in the third quadrant and $f(α)= \frac{\sin \left( \frac{3π}{2}-α\right)\cos \left( \frac{π}{2}-α\right)\tan \left(-α+π\right)}{\sin \left( \frac{π}{2}+α\right)\tan \left(2π-α\right)}$,

(1) Simplify $f(α)$

(2) If $\cos α=- \frac{5}{13}$, find the value of $f(α)$.

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