
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 $ABC$, it is known that vector $\overrightarrow{a} = (\sin A, 1)$, $\overrightarrow{b} = (\cos A, \sqrt{3})$, and $\overrightarrow{a} \parallel \overrightarrow{b}$.

(1) If $\sin\varphi = \frac{3}{5}$, $0 < \varphi < \frac{\pi}{2}$, find the value of $\cos(\varphi - A)$;  
(2) If the area of $\triangle ABC$ is 2, and $AB = 2$, find the length of $BC$.

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