Exercise 1 solution

(a) A full circle is 360 degrees, so a quarter turn is 90 degrees.
    North = 0 (or 360), East = 90, South = 180, West = 270.
    South-west is halfway between south and west: (180 + 270) / 2 = 225 degrees.

(b) Back bearing = bearing + 180 (if the answer is over 360, subtract 360).
    - 60 degrees  -> 60 + 180 = 240 degrees
    - 300 degrees -> 300 + 180 = 480, minus 360 = 120 degrees
    - 175 degrees -> 175 + 180 = 355 degrees

(c) Two bearings of 350 and 20 degrees: the shortest turn from 350 to 20 is
    through north: 10 degrees to reach 360 (north), then 20 more = 30 degrees
    to the right. Going the other way round would be 330 degrees, which is
    the long way.