In Eratosthenes' method of finding the circumference of a planet, when at noon a vertical stick at the Equator casts no shadow, a vertical stick 2,500 kilometers away casts a shadow and makes an angle of 40o with the rays of the Sum. What is the circumference of this planet?

24,901 miles.

Explanation:

The circumference is the distance of the earth that is measured around the poles. Eratosthenes method of finding the circumference of a planet with the sun's rays cast a shadow on the equator a vertical stick of 2,500 km making an angle of 40° with the planet shows a distance of 40,075.017 km. He also estimates that the meridian has a length of 252, 000 stadia. And described these techniques in his book measure of the earth.

It is useful for historians to write narratives so that history can be passed on from their point of view.  think about a story being told in third person, then think about it again being told in first person, by someone who actually experienced the event.