The Basic VMG Calculation

Understanding VMG (velocity made good) is essential if you want to sail your boat quickly from point to point.  This is true regardless of whether your boat is real or virtual.
VMG values are used in many 'advanced' racing tactics, but the calculation of these values remains the same.

From a 'trig' standpoint, it should be obvious to you that VMG = BtSpd * COS(40*).
Easy enough to let a spreadsheet or scientific calculator tell you the actual value of the Cosine.
You don't need to know the actual values of the trig function.
But the fundamental relationship between BtSpd and VMG should be clear.

If not, you can go to Google for help.
And, of course, you can comment on this blog.