Need to find approximate area of Earth using angular distance?

[reallybadattrig]

Hello, I really needed help with my trig homework so this forum is my last hope.

The gist of the question is:
a) Choose two points on the same longitude or equator to calculate the angular distance between the two.
b) Using a) find the radius of the Earth
c) Calculate the surface area of the Earth.

So for a) I chose 0° 20°E and 0° 65°E which should make the angular distance 45° right? I'm stuck there. I don't know how to find the radius because I don't know how to find the arc length since I don't have the radius. Please help!

 

[Deleted member 4993]

Hello, I really needed help with my trig homework so this forum is my last hope.

The gist of the question is:
a) Choose two points on the same longitude or equator to calculate the angular distance between the two.
b) Using a) find the radius of the Earth
c) Calculate the surface area of the Earth.

So for a) I chose 0° 20°E and 0° 65°E which should make the angular distance 45° right? I'm stuck there. I don't know how to find the radius because I don't know how to find the arc length since I don't have the radius. Please help!

Please post the COMPLETE problem (and its context - such as which subject - what level - etc.) - not just a gist.

 

[reallybadattrig]

Ah sorry my bad. It's for Year 11 high school maths and a homework question.

I guess I should clarify that a) is: Choose two points on the same longitude or equator on the Earth to calculate the angular distance between the two points. (I just omitted 'on the earth' and 'between the two points' because I thought it wasn't necessary)

I probably shouldn't have used 'gist' when what I posted was the complete question. ?

 

[Dr.Peterson]

It seems to me that you can't answer any of the questions without some actual information about the points. In particular, to find the radius of the earth, you will need some sort of distance information. Are you perhaps supposed to choose two points for which you know not only latitude and longitude, but also the distance between them?

This makes me think of Eratosthenes' calculation of the size of the earth based on two points on (approximately) the same meridian, the difference in sun angle between them (which amounts to the difference in latitude), and the actual distance between them.

Please quote the entire problem as given to you (not just part a), including whatever it means by "choose" -- it has to mean more than pointing to them on the globe, or just picking some arbitrary numbers. If that is all it said, then it is a poorly worded question, and you have to ask your teacher what it means.

 

[reallybadattrig]

^I asked my teacher today. She said we needed to use google earth. I guess I wasn't the only one confused because a few other classmates also asked for clarification. The question was really structured like that:
3a) ......
b) .....
c) ......

I still don't know how to find the arc length/radius using just the chord and angle though. Because presumably, I would need to find the arc length to find the radius?

 

[Dr.Peterson]

^I asked my teacher today. She said we needed to use google earth. I guess I wasn't the only one confused because a few other classmates also asked for clarification. The question was really structured like that:
3a) ......
b) .....
c) ......

I still don't know how to find the arc length/radius using just the chord and angle though. Because presumably, I would need to find the arc length to find the radius?

Please, please, please, tell us the actual wording of the entire problem, and what your teacher said in response to these queries! You seem to be deliberately refusing.

As I read it, there are no chords involved. What were you expected to find using Google Earth? I'd expect you to find the distance (along the surface of the earth, not along a chord through it) between two points, along with their latitude and longitude.

Have you learned about Eratosthenes?