
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 a frustum with top and bottom base radii of $1$ and $\sqrt{3}$ respectively, and a height of $1$. Let the centers of the top and bottom bases be $O'$ and $O$. Two mutually perpendicular axial cross-sections are $A B B' A'$ and $C D D' C'$. Find the angle between the line $D' O$ and $O' A$.

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