Finding the sides of a right spherical triangle

  • Context: Undergrad 
  • Thread starter Thread starter lilcoley23@ho
  • Start date Start date
  • Tags Tags
    Spherical Triangle
Click For Summary

Discussion Overview

The discussion revolves around finding the lengths of the sides of a right spherical triangle given its angles, specifically one angle of 90 degrees and the other two angles measuring 50 and 70 degrees. Participants explore various formulas and approaches related to spherical triangles, including the sine formula, cosine formula, polar cosine formula, cotangent formula, and Napiers formula.

Discussion Character

  • Exploratory
  • Technical explanation
  • Homework-related

Main Points Raised

  • One participant seeks assistance in solving for the lengths of the sides of a spherical triangle given the angles, expressing uncertainty about where to begin.
  • Another participant suggests looking up Girard's theorem as a potential aid in the problem.
  • A later reply clarifies that Girard's theorem relates to the area of a spherical triangle, questioning whether finding the area is necessary to determine the side lengths.
  • Another participant introduces the Haversine formula as relevant to the problem, indicating a shift in focus from area to arc length.
  • One participant expresses confusion about applying the Haversine formula, particularly regarding the variables involved and how to proceed without knowing the lengths of sides a, b, or c.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus on the best approach to solve the problem, with multiple competing views on which formulas and theorems are applicable.

Contextual Notes

There is uncertainty regarding the relationship between the area of the triangle and the lengths of the sides, as well as the application of the Haversine formula without known side lengths.

Who May Find This Useful

Individuals interested in spherical geometry, particularly those looking to solve problems involving spherical triangles and their properties.

lilcoley23@ho
Messages
19
Reaction score
0
I need some help with spherical triangles. I am looking for the lengths of the sides of a spherical triangle given that all the angles. One being 90 degrees and the other 2 angles being 50 and 70 degrees. I don't even know how to go about solving this. I know there are 4 formulas for solving these tyle of problems the sine formula, the cosine formula, the polar cosine formula, and the cotangent formula. I also saw something called Napiers formula where you might use a pentagon to show the relationship of angles to sides so maybe I can find an answer with that. I have no idea where to begin to sove this, nor can I find a single example to follow. Please Help!
 
Physics news on Phys.org
Look up Girard's theorem that should help you.
 
Thanks so much for a response!

Girards formula gives me formulas for the area of a spherical triangle. Do I have to find the area in order to find the length of the sides? Do you know where I can see examples of solved problems like this. I can't find a single one.
 
Sorry, for some reason I was thinking area and not radian arc length, what you are looking for is the “Haversine formula”

I think you will find some examples in Wiki.
 
So the Haversine formula states that cos(c) = cos(a)cos(b) + sin(a)sin(b)sin(C)

I for all of this formula all I really know is C for each formula. So if I have 50 degrees, do I write that the side opposite of that is:

cos(50) = (cos(a)cos(b) - cos(c))/(sin(a)sin(b))

I don't see how I can figure it out anymore than that not knowing what a b or c is? I'm so lost with this stuff!
 

Similar threads

  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 8 ·
Replies
8
Views
3K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 7 ·
Replies
7
Views
3K
  • · Replies 9 ·
Replies
9
Views
4K
  • · Replies 2 ·
Replies
2
Views
2K
Replies
6
Views
2K
  • · Replies 8 ·
Replies
8
Views
4K
Replies
2
Views
1K