
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
Consider two points on the surface of a perfect spherical Earth: point \(A\) is at \(0^\circ\) latitude and \(90^\circ \text{ E}\) longitude, and point \(B\) is at \(30^\circ \text{ N}\) latitude and \(80^\circ \text{ W}\) longitude. Calculate the angle \(\angle ACB\) formed at the Earth's center \(C\).

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