How was the size of earth first measured?

Answer 1

Eratosthenes an Egyptian mathematician was first to estimate Earths circumference. about 2200 years ago.

He found that on summer solstice day Sun was visible in a deep well..He knew that on the same day in his hone town that day Sun made a n angle. THe town was about 800 KM from the place were the well was located. He measured the shadow the sun made on a vertical stick tio be 7.2 degree.
So the angle 7.2 for 800 kilometers.

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Answer 2

Nova Adams

The size of Earth was first measured using angular measurements of the Earth's shadow during a lunar eclipse by the ancient Greeks.

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.