
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
Among the following five propositions:  
① If $a \perp b$, $b \perp c$, then $a \perp c$;  
② If $a$, $b$ form equal angles with $c$, then $a \parallel b$;  
③ If $a \parallel \alpha$, $b \parallel \alpha$, then $a \parallel b$;  
④ If $\alpha \cap \beta = l$, $a \subset \alpha$, $b \subset \beta$, then $a$, $b$ are parallel or skew;  
⑤ If within plane $\alpha$ there are three points not on the same line that are equidistant from plane $\beta$, then $\alpha \parallel \beta$;  
Among the above propositions, the incorrect ones are     . (Fill in the serial number only)

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