
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
In triangle $ABC$, let $a, b, c$ be the lengths of the sides opposite to angles $A, B, C$ respectively, and satisfy the equation $(a+c)(\sin A - \sin C) = \sin B(b-c)$.  
(1) Determine the measure of angle $A$.  
(2) If $f(x) = \sqrt{3}\sin x\cos x - \cos^2 x + \frac{1}{2}$, find the range of $f(B)$.

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