
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
(1) Calculate the value of $\sin ^{2}120^{\circ}+\cos 180^{\circ}+\tan 45^{\circ}-\cos ^{2}(-330^{\circ})+\sin (-210^{\circ})$  
(2) Given $\sin (\pi+\alpha)= \frac {1}{2}(\pi < \alpha < \frac {3\pi}{2})$, find the value of $\sin \alpha-\cos \alpha$.

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