
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 line $Ax+By+C=0$ intersects the circle $x^2+y^2=9$ at points $P$ and $Q$, where $A^2$, $C^2$, and $B^2$ form an arithmetic sequence, and $O$ is the origin of the coordinate system, then $\overrightarrow{OP} \cdot \overrightarrow{PQ} = \_\_\_\_\_\_$.

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