🔍 Key Concepts

• On a course of 270° (due west), your latitude stays the same and only longitude changes • Relationship between difference of longitude (DLo), distance steamed, and departure at a given latitude • Conversion between nautical miles and minutes of longitude at a mid-low latitude

💭 Think About

• What is the sign of the longitude change when you steam west from a point in the Western Hemisphere? Does the longitude number increase or decrease? • At latitude 38°12'S, is 1 minute of longitude equal to 1 nautical mile, or do you need to apply a cosine of latitude? How does that affect the distance-longitude conversion? • Once you compute the change in longitude (in degrees and minutes), how do you correctly add or subtract it from the starting longitude to get the arrival longitude?

✅ Before You Answer

• Confirm that latitude remains 38°12'S for the whole leg because you are on a due west course • Compute DLo in minutes first, then convert to degrees and minutes before combining with the starting longitude • Make sure the final longitude is still in the Western Hemisphere and the arithmetic of adding/subtracting minutes is done carefully (borrowing/carrying where needed)