I'm trying to study how to find the distance between two points if their latitudes and longitudes are given.
I have a question about the proof of part of the haversine formula given at Math Forum. It says that the length of chord AD, two points at the same latitude, lat1, on a sphere of radius 1, is
2*sin(dlon/2)*cos(lat1)
but I couldn't get how they obtained it. Could you help me?
2*sin(dlon/2)*cos(lat1)
.