🔍 Key Concepts

• Mid-latitude sailing formula for course and distance • How to find the mean latitude between two positions • Relationship between difference of longitude (DLo), difference of latitude (DLat), and departure

💭 Think About

• First, compute the difference in latitude and the difference in longitude between the two positions. Are they north/south and east/west? • Use the mean latitude to adjust the difference in longitude. How does cosine of mean latitude come into the departure calculation? • After finding the departure and DLat, which basic right-triangle trigonometric functions give you the course angle and the hypotenuse (distance)?

✅ Before You Answer

• Be sure to convert minutes of arc to nautical miles correctly (1 minute of latitude = 1 NM). • Confirm that you used mean latitude in degrees, not radians, when taking the cosine on a calculator. • Check whether the resulting course should be in the NE, SE, SW, or NW quadrant based on the signs of DLat and DLo before converting to true bearing.