
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
If ${\overrightarrow{e}_1},{\overrightarrow{e}_2}$ are unit vectors with an angle of $90^{\circ}$ between them, calculate the angle between $\overrightarrow{a}=2{\overrightarrow{e}_1}+{\overrightarrow{e}_2$ and $\overrightarrow{b}=3{\overrightarrow{e}_1}-{\overrightarrow{e}_2}$.

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