
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 the following propositions:
1. The contrapositive of "If $b^2-4ac>0$, then the quadratic equation $ax^2+bx+c=0$ has real roots";
2. The converse of "A quadrilateral with equal sides is a square";
3. The negation of "If $x^2=9$, then $x=3$";
4. The converse of "Vertically opposite angles are equal", among which the true propositions are

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