
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
The correct number(s) of the following conclusions is/are $\boxed{\text{answer}}$.

(1) If $\overrightarrow {a}$ and $\overrightarrow {b}$ are both unit vectors, then $\overrightarrow {a}$ = $\overrightarrow {b}$;

(2) In physics, an action force and a reaction force are a pair of collinear vectors;

(3) A vector with a direction of southwest 60° and a vector with a direction of northeast 60° are collinear vectors;

(4) The x-axis and y-axis on the rectangular coordinate plane are both vectors.

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