
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
Given that $A$, $B$, $C$ are the three internal angles of $\triangle ABC$, $\overrightarrow{a}=(\sin B+\cos B,\cos C)$, $\overrightarrow{b}=(\sin C,\sin B-\cos B)$.
(1) If $\overrightarrow{a}\cdot \overrightarrow{b}=0$, find angle $A$;
(2) If $\overrightarrow{a}\cdot \overrightarrow{b}=- \frac {1}{5}$, find $\tan 2A$.

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