1 knot = 1 nautical mile per hour
let the horizontal displacement =
distance from the lighthouse =
using Pythagoras ...
a sailboat is moving at 6 knots (nautical miles) due east on a course which will take it 5 knots south of a lighthouse. when the boat is 13 miles from the lighthouse....
a) how fast is the boat approaching the lighthousee
b) how fsst is the boat's azimuth angle changing for an observer in the lighthouse