
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 given that $\cos A= \frac{5}{13}$, $\tan \frac{B}{2}+\cot \frac{B}{2}= \frac{10}{3}$, and $c=21$.
1. Find the value of $\cos (A-B)$;
2. Find the area of $\triangle ABC$.

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