If you find the maths complex in http://williams.best.vwh.net/avform.htm

then I suggest:

a) plenty of scrap paper and pencil
b) remember that Excel works in radians not degrees: 2 pi radians = 360
degrees
c) make sure that you fully understand sin, cos, tan (and their inverses)
d) solve some simple examples using paper and spreadsheet eg wind 10 kph at
90 degrees to course, XC speed 60 kph.

as you make the examples more difficult, draw the triangles on paper and
then create right angle triangles which will help you to solve the problem
eg wind 10 kph at 45 degrees to course headwind/tailwind.

e) if still going, try to answer your original query - may need to add
180/360 or work modulo 360 at intervals.

Now you should be able to understand the Aviation Formulary.

If you still want a challenge, try solving for varying climb rates and
varying glide rates, and an overall height change.

I have just been solving the latter equations for a 300km task to find:
i) most important is the climb rate achieved - this outweighs all other
factors
ii) the start/finish height loss is important and especially the leg on
which it is applied (best into wind)
iii) for a modern glider, winds below 10 kt are relatively benign
iv) with stronger winds some courses are better than others:
a crosswind Out/Return is better than a triangle which is better than a
with/into wind Out/Return.
v) as is already known, the glide speed is not too critical and can be too
fast.

ps: I dont fly very fast.
Rory