Hi
You may (or may not) be interested in plotting circles such as the ones shown on the second link in my post below :
http://www.pprune.org/professional-p...ml#post9648882 (the figure was not modified to fit your case, just consider the 62° parallel and its intersection with the 30W and the 10W meridians)
Then you will be able to see for yourself exactly how this all works in Google Earth
You will be able to see that halfway between, your gyro track of 85.7 gives you a true track of 90° and that your true track upon arrival will be 94.3
Your average true track will be exactly 90°
Hope this clarified the situation as opposed to making it more confused.