I am a Math student and don't know about longitude and latitude. This question was asked in CSIR-NET Mathematics. Please help me to solve it.
Two points $A$ and $B$ on the surface of the Earth have the following latitude and longitude co-ordinates:
A: $30^\circ $ N , $ 45^\circ$ E
B: $30^\circ $ N , $ 135^\circ$ W
If $R$ is the radius of the Earth, what is the length of the shortest path from $A$ and $B$?