RP,
These questions both ask you for the rhumb line track along a line of latitude.
What they are after is the departure i.e. the distance between two points.
Departure = ChLong x Cos Lat
Q1. Departure = 42 (degrees between the two points) x Cos 65 (latitude)
= 16.9 (degrees at correct scale) x 60
= 1014 nm
I'd therefore go for answer a) as it's closest.
Q2. Here they want you to rearrange the Departure formula to obtain ChLong to find the new longitude.
Departure = ChLong x Cos Lat
ChLong = Departure / Cos Lat
ChLong = (1200 / 60) / Cos 32 (1200 is divided by 60 to get it into degrees)
= 23:35
So E020 + 23:35 = E43:35 which is answer b).
You use Convergency as soon as great circles are mentioned. Departure is used on rhumb lines.
Hope that helps.
SM.
Last edited by SunderlandMatt; 8th June 2012 at 10:20.
Reason: Edited to remove any mention of straight lines, as pointed out by W1.