🔍 Key Concepts

• Mercator sailing and the relationship between difference of longitude, meridional parts, and distance on a given course • Using course and distance to find departure and difference of longitude on a Mercator chart • How latitude affects the conversion from departure to difference of longitude (mean latitude or meridional parts)

💭 Think About

• What trigonometric relationship connects the distance run, the course (282°T), and the departure? Which function of the course should you use? • Once you have the departure, how do you convert that to difference of longitude on a Mercator sailing, taking into account the starting latitude in the Southern Hemisphere? • After finding the numerical difference of longitude, in which direction (east or west) will your longitude change when you steam on course 282°T from an initial longitude of 18° 23' E?

✅ Before You Answer

• Be sure you are using Mercator sailing, not plane sailing – use meridional parts or the proper mean latitude relationship. • Check that your course 282°T is correctly interpreted as a west-going course with a certain north/south component; confirm the sign of your longitude change (E to W). • After computing the new longitude, verify that you convert decimal minutes/seconds correctly into degrees and minutes when comparing to the answer choices.