
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 $| \overrightarrow{a}|=4$, $| \overrightarrow{b}|=3$, and $(2 \overrightarrow{a}-3 \overrightarrow{b}) \cdot (2 \overrightarrow{a}+ \overrightarrow{b})=61$：
1. Find the angle $θ$ between vectors $ \overrightarrow{a}$ and $ \overrightarrow{b}$;
2. Calculate $| \overrightarrow{a}+2 \overrightarrow{b}|$.

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