
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 $sin^2 120^\circ + cos 180^\circ + tan 45^\circ - cos^2 (-330^\circ) + sin (-210^\circ)$  
(2) Given $α, β \in (0, π)$, $tan(α-β) = \frac{1}{2}$, $tanβ = -\frac{1}{7}$, find the value of $2α-β$.

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