
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 propositions, the true ones are:

1. The probability of a certain event is equal to 1.
2. The converse of the proposition "If $b=3$, then $b^2=9$".
3. Complementary events are necessarily mutually exclusive events.
4. The contrapositive of the proposition "Corresponding angles of similar triangles are equal".

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