# What is the distance, measured along a great circle, between locations at #(34^o N, 34^o W) and (34^ S, 34^o E)#?

##### 1 Answer

#### Explanation:

South latitudes and West longitudes are negatives.

In spherical-polar coordinates, the position vectors to the

locations

of the Earth are

For unit vectors #n_(OP) and n_(OQ), omit the factor 6371 km (mean

radius of the Earth ). in these normal directions

The angle subtended by the great-circle arc PQ at the center is

The great-circle arc distance PQ = 6371 X alpha in radians#