
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}
user