
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 vector $$\overrightarrow {a}$$\=$$(1， \sqrt {3})$$, vector $$\overrightarrow {b}$$ is a unit vector, and $$\overrightarrow {a}$$• $$\overrightarrow {b}$$\=1, then the angle between 2 $$\overrightarrow {b}$$\- $$\overrightarrow {a}$$ and 2 $$\overrightarrow {b}$$ is \_\_\_\_\_\_.

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