
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 Earth, assumed to be a perfect sphere with radius 1. Point $A$ is located at $30^\circ \text{ N}$ latitude and $90^\circ \text{ E}$ longitude, and point $B$ is located at $60^\circ \text{ N}$ latitude and $100^\circ \text{ W}$ longitude. What is the degree measure of $\angle ACB$, where $C$ is the center of the Earth?

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