Help with Eratosthenes' Astronomical Measurement!

[monkeymocha]

Astronomy Help! :(

I'm sure that compared to all the other problems posted here, this Astronomy problem is incredibly easy, but I'm TERRIBLE at sciences and mathematics and really need some help.

The problem is: "Although the distance to the Sun is obviously much larger than the distance between Alexandria and Syene, it is not infinite. This results in a small error in Eratosthenes' measurement, which is given by the difference in the angle of the Sun between Alexandria and Syene. What is the difference in the angle in degrees? (assume a distance between Alexandria and Syene of 860 km. It may help to draw a diagram.)"

The answer choices are:
a) 3.29 x 10^-4 degrees
b) 2.07 x 10^-3 degrees
c) 5.75 x 10^-6 degrees
d) 0.329 degrees
e) 3.29 x 10-2 degrees


This problem is referring to how Eratosthenes measured the circumference of the Earth by using the distance from Alexandria and Syene and the angles of the sun. See http://www.eg.bucknell.edu/physics/astronomy/astr101/specials/eratosthenes.html for details.

I honestly have no idea where to even begin. I'm not even sure what the problem is even asking. If anyone could just point me on the right track, I would really be happy! Thank you!

 

[Borek]

Draw the diagram (Sun and both cities). There is a triangle that contains angle in question.

--
methods