Area between two longitudes?

Question

I am trying to compute the area between two longitudes (using the angle between them) but am having a hard time. I can do that more easily between latitudes but longitude reveals to be tricky. Anyone has a good reference formula for that one?

Answer 1

Assume that the angle is 30°.

The the ares between is 30 / 360 or 1 / 12 of the surface area of the earth.