
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
Simplify the following expressions:  
1. $\dfrac {\cos (\alpha- \dfrac {\pi}{2})}{\sin ( \dfrac {5\pi}{2}+\alpha)}\cdot \sin (\alpha-2\pi)\cdot \cos (\pi-\alpha)$;  
2. $\sqrt { \dfrac {1+\sin \alpha}{1-\sin \alpha}}- \sqrt { \dfrac {1-\sin \alpha}{1+\sin \alpha}}$, where $\alpha$ is an angle in the third quadrant.

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