Finding Circumference Of A Parallel Of Latitude

With an equatorial radius of the earth of 3444 nm find the circumference of a parallel of latitude 30° N.

Given:

Latitude 30° N
Earth's radius = 3444 nautical miles

What is asked:

Circumference of a parallel at latitude 30° N.

Solution:

Circumference = 2πr × Cos Lat 
                           = 2 × 3.1416 × 3444 nm × Cos 30°
                           = 18740.2 nm