Consider triangle A (45ºN010ºW), B (48º30'N015ºW), C (45ºN015ºW).

You have calculated that side AC is 210nm.

Side BC is also 210nm: change of latitude = (3x60) + 30 = 210nm.

It is an isosceles triangle and angles CBA and BAC are equal.

Angle BCA is 90º (meridian crossing parallel of latitude) so angles CBA and BAC must be 45º.

The track from A to B is 270º + angle BAC = 270º + 45º = 315ºT

 

Rhumb lines are straight lines on a Mercator:

 

 

                        015ºW                                   010ºW

 

            48º30’N

 

                                45º

 

            3x60 + 30

            = 210nm

 

 

 

            45º00’N        90º                           45º                  Track = 270º + 45º

                                                                                                = 315ºT

                                 Departure = 5 x 60 x cos 45º

                                                = 212nm