It's a fact.

Many facts are wrong/untrue. Facts are merely what your authority tells you are facts. You believe it is a fact (i.e. true).

However, your "proof" is circular.

Premise : The world is a sphere because equations which include its sphericity work to predict sunrise/sunset times.
Conclusion : The equations work because the world is spherical.

The premise IS the conclusion, and does not follow from it. It's circular logic.

If the Earth is flat, why does the formula work?

Because we built it to! It coincides with the actual measurements that we made of the sunset/sunrise times because it was built from / confirmed against such charts.

Our conception of the world and its workings can be (and most often are) entirely wrong and still be useful.

Why can you not produce these "charts" that you claim exist

I won't because i don't do people's homework for them - it makes them worse students/researchers. If you earnestly search for such charts and fail to find them, then we can talk about what you tried and i will do my utmost to help you. Finding charts of the sunrise and sunset times should not be difficult.

Charts do not require the world to be any particular shape, just like the times for sunrise and sunset within them. They simply are.

It's a fact.

Many facts are wrong/untrue. Facts are merely what your authority tells you are facts. You believe it is a fact (i.e. true).

However, your "proof" is circular.

Premise : The world is a sphere because equations which include its sphericity work to predict sunrise/sunset times. Conclusion : The equations work because the world is spherical.

The premise IS the conclusion, and does not follow from it. It's circular logic.

If the Earth is flat, why does the formula work?

Because we built it to! It coincides with the actual measurements that we made of the sunset/sunrise times because it was built from / confirmed against such charts.

Our conception of the world and its workings can be (and most often are) entirely wrong and still be useful.

Why can you not produce these "charts" that you claim exist

I won't because i don't do people's homework for them - it makes them worse students/researchers. If you earnestly search for such charts and fail to find them, then we can talk about what you tried and i will do my utmost to help you. Finding charts of the sunrise and sunset times should not be difficult.

Charts do not require the world to be any particular shape, just like the times for sunrise and sunset within them. They simply are.