Ogygos Wrote:
....
> -10.892222, -77.520556
> 51.975516, -1.570832
...
> delta = 10007.6017 km
> 90.0005 degrees
>
> azimuth = 36.8743 degrees (from pt1 to pt2)
> 252.3322 degrees (from pt2 to pt1)"

Which calculator produced this result?

========
Rollright Stone Circle = 51.975531, -1.570829
Caral Greater Pyramid = -10.890212, -77.52134

[www.satsig.net]
azimuth = 252.29
range = 10,022.987 km

========
Using the ‘Haversine’ formula":
[www.movable-type.co.uk]
10020 km
252.29 bearing at Rollright
36.70 bearing at Caral

========
Using spherical trig
[jqjacobs.net]
arc: 90.1135 degrees
bearings: -107.708, 36.696