Meridian curves of surfaces of revolution are geodesics

Question

Could someone explain how to go about proving that the meridian curves on a surface of revolution are geodesics?

Answer 1

Hint: At any point along a geodesic, the normal of the geodesic is parallel to the normal of the surface.

Answer 2

Alternative hint: A meridian is is the set of fixed points for a particular isometric transformation of the surface. Isometries preserve geodesics. At every point on a smooth surface, there is exactly one geodesic in each direction.