You are
looking at a direct track between WP1 and WP3.
The aircraft flies from WP1 to WP2 then from WP2 to WP3. All Waypoints are on
the same line of latitude, which would be the Rhumb Line Track between the
three waypoints.
The question is 'Does an INS governed course follow a Rhumb Line Track?'.
Answer = No, it follows a Great Circle Track which is on the Polar side of the
Rhumb Line Track.
In the question the aircraft changes from one Great Circle Track to another
Great Circle Track at WP2.
Draw a diagram - you will see this clearly.