Question 600886
A plane is flying at an altitude of about 7 miles above Earth. What is the measure of the arc that represents the part of Earth you can see? The radius of Earth is about 4000 miles. 
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The plane's distance from the Earth's center is 4007 miles.
The distance on the surface of Earth is 4000 miles.
The distance from the plane to the horizon is the 3rd leg of a right triangle.
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{{{d = sqrt(4007^2 - 4000^2)}}}
d =~ 236.75 miles
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The arc on the surface is close to that.
The angle A at Earth's center = arccos(4000/4007) =~ 3.3872 degs
The arc is {{{2*pi*r*(A/360)}}}
=~ 236.47 miles each direction
x2 --> 472.94 miles
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