Longitude problem on a Terrestrial Sphere

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SUMMARY

The discussion centers on calculating the distance between two points on the equator based on a 1-degree difference in longitude. The correct distance is approximately 69.1 miles, derived from the formula S = rθ, where the Earth's radius is taken as 3959 miles. Variations in the radius value, such as Google's 3963.1676 miles, yield slightly different results, with a distance of 69.2 miles. The key takeaway is the importance of using the correct radius for accurate calculations.

PREREQUISITES
  • Understanding of spherical geometry
  • Familiarity with the formula S = rθ
  • Knowledge of Earth's radius values
  • Ability to convert degrees to radians
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  • Research the implications of using different Earth radius values in calculations
  • Learn about spherical trigonometry and its applications
  • Explore the effects of latitude on distance calculations
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Students studying geometry, educators teaching Earth sciences, and anyone interested in geographical calculations involving longitude and distance on a spherical surface.

Equilibrium
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Homework Statement


How far apart (in miles) are 2 points on the equator if their longitudes differ by 1 degree?
The correct answer is 69.8 miles, I'm not sure if typo

Homework Equations


S=r\theta
radius of Earth = 3959 miles

The Attempt at a Solution


\theta = 1\deg*\frac{\pi}{180}
S=3959*\frac{\pi}{180}
S = 69.1 miles
 
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Nothing wrong with your working, except that you should be more clear that you're starting by converting theta into radian measure. But your answer is right.

The difference could be because of the value you're supposed to use for the Earth's equatorial (great circle) radius. Are you given a value you're supposed to use?

The value you quoted looks quite OK, but google's is slightly different: 3 963.1676 miles, and yields a slightly different answer (69.2mi, still closer to yours than the expected one).
 
thanks for verifying
 

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