Depends what the great circle function does. But chances are it gives you the arc length between the two points, which would give you the shortest distsnce between them on the surface of the earth.
If you wanted the distance through the earth you would need to work put the central angle of that arc, then use that to work out the remaining edge of the triangle formed between the two cities and the centre of the earth.
Depends what the great circle function does. But chances are it gives you the arc length between the two points, which would give you the shortest distsnce between them on the surface of the earth.
If you wanted the distance through the earth you would need to work put the central angle of that arc, then use that to work out the remaining edge of the triangle formed between the two cities and the centre of the earth.