You only need elementary trigonometry to do this question if you use the guidance given in the hints.

London is at longitude 0^o and latitude 51.5^o North and Sydney at longitude 151^o East and latitude 34^o South. Taking the earth to be a sphere with radius 6378 kilometres, calculate the distance between London and Sydney.

If the flight path is the shortest route at an altitude of 6 kilometres calculate the distance along the flight path.