On 17 Mar, 12:30, Bob Cook wrote:

But we should add (vector addition) the force of gravity (downward) the to
force of lift (upward and rearward).

We find that these two forces nearly cancel each other except for a
realtively small resultant force, parallel to the line of flight.

This resultant force could be added to drag, therefore thrust would have
to be the sum of this force plus drag, but in the opposite direction.

Agreed.

Ian