
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
In the diagram, $O$ is the center of the larger circle with an area of $81\pi$. A smaller circle is inside the larger one and its topmost point touches the center of the larger circle. Each circle is divided into two equal areas. Calculate the total area of the shaded regions.

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