" The displacement of track from the N60 Latitude would be proportional to the Sine of the Change of Longditude. The Sine of 60 degrees is 0.5; therefore, the Convergency is 30 degrees. The Initial True Track is half the convergency = 285 degrees. "
In case it wasn't clear, that's an approximation. (Also a typo.) Initial track for a change in longitude of 60 degrees will actually be 296.6 deg; for a change of 40 deg in longitude it will be 287.5 deg.