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Name:  rexann r mallory
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Date: 1999

What is the distance around the earth at 23 1/2 degrees north?

First, let's calculate the distance around the earth at the equator. The distance around a circle is also called the circumference. The circumference is given by 2 times pi times the radius, where pi is 3.14. The radius of the earth at the equator is about 6378 kilometers so the distance around the earth at the equator is 2 time 3.14 times 6378 which equals 40,074 kilometers.

Now imagine if we were to slice through the earth at 23.5 degrees north. This slice would be a circle whose circumference we wish to calculate. The radius of this circle will be smaller than the radius at the equator. How much smaller? The radius at 23.5 degrees north will be the radius at the equator times the cosine of the latitude. So the radius at 23.5 degrees north is 6378 times cosine(23.5) which is 5849 kilometers. The distance around the earth at 23.5 degrees north is then 2 times 3.14 times 5849 which is 36,750 kilometers. Hope you followed that- it's a little hard to explain without being able to draw a picture.

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