
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 Earth O has a radius of R, and P and Q are two points on the Earth, with P at 45°N, 20°E, and Q at 45°N, 110°E, the spherical distance between P and Q is __________.

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