
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 $a$, $b$, $c$ are three distinct lines, and $α$, $β$, $γ$ are three different planes, the following five propositions are given:

$①α//γ$, $β//γ \Rightarrow α//β$;   $②a//α$, $b//α \Rightarrow a//b$;

$③α \perp γ$, $β \perp γ \Rightarrow α//β$;   $④a \perp c$, $b \perp c \Rightarrow a//b$;

$⑤$ If $a//b$, $α//β$, then the angle formed by $a$ and $α$ is equal to the angle formed by $b$ and $β$.

Determine the sequence number of the true propositions.

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