July 2nd, 2017, 12:13 PM  #1 
Newbie Joined: Jul 2017 From: moscow Posts: 2 Thanks: 0  Spherical triangle
I want to find angles of spherical traingle. The geographical coordinated of the points are 0, 0 0.000001, 0 0, 0.000001 I expect that agnles will be 90, a bit more than 45 and a bit more than 45 degrees. I use great circule distance formula and spherical cosine formula https://en.wikipedia.org/wiki/Greatcircle_distance https://en.wikipedia.org/wiki/Spherical_law_of_cosines The central angles are pretty small and they seems correct. They are 2,46827E8 1,74533E8 1,74533E8 But spherical law of cosines give strange results. I got the following angles in radians 0,687 0,687 1,9438 or in degrees 39,3627 39,3627 111,3746 It seems there is a mistake. Could you please help me. 
July 2nd, 2017, 02:02 PM  #2 
Global Moderator Joined: May 2007 Posts: 6,305 Thanks: 525 
It would be helpful if you showed intermediate results.

July 3rd, 2017, 05:03 PM  #3  
Global Moderator Joined: May 2007 Posts: 6,305 Thanks: 525 
You need to specify the radius of the sphere. Quote:
 
July 4th, 2017, 12:06 PM  #4 
Newbie Joined: Jul 2017 From: moscow Posts: 2 Thanks: 0 
Yes. They are central agnles in radians

July 4th, 2017, 12:40 PM  #5 
Global Moderator Joined: May 2007 Posts: 6,305 Thanks: 525  Central angles of what? Try to be specific. Also you need a radius for the sphere (1?). Last edited by mathman; July 4th, 2017 at 12:49 PM. 
July 5th, 2017, 05:21 PM  #6 
Global Moderator Joined: May 2007 Posts: 6,305 Thanks: 525 
I will assume the central angle is with reference to center of the sphere with radius 1. In that case the two equal sides have angles exactly equal to the sides (0.000001). The third side is very slightly less than sqrt(2) times other side length.


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law of cosines, spherical, triangle 
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