🔍 Key Concepts

• Difference of Latitude (DLat) and Difference of Longitude (DLo) between departure and destination • Mid-latitude sailing formula: use the average latitude to convert longitude difference to departure (east‑west distance) • Relationship between course angle, north‑south distance, and east‑west distance in a right triangle

💭 Think About

• First, determine whether you are going mainly southeast, southwest, northeast, or northwest based on the starting and ending latitudes/longitudes. How does that affect the true course quadrant? • Compute the difference of latitude in minutes of arc. Then compute the difference of longitude, convert it to minutes of arc, and adjust it using the cosine of the mid-latitude. Which answer choices have a course roughly matching the ratio of E‑W to N‑S distance? • Once you have north‑south and east‑west components, use right‑triangle relationships (Pythagorean theorem and tangent) to estimate the distance and course. Which choice best matches both your distance and course direction?

✅ Before You Answer

• Be sure you are using mid‑latitude (average of the two latitudes), not just the starting latitude, when applying cosine to the longitude difference. • Confirm that all angular values used in trigonometric functions are in degrees, and that you convert degrees and minutes to a single unit (usually minutes) before forming the triangle. • After finding the course angle from the meridian (north‑south line), check that the final true course is expressed in three digits and lies in the correct SE/SW/NE/NW quadrant based on your start and end positions.