Golf pro P.J. Cowan -- who's a swing coach for players of all ages -- shared the footage of a round with #45 this week ... showing off a perfect view of one of POTUS' drives.

You can see in the clip ... Donald PIPES the golf ball -- which is kind of surprising, given the uneasiness of his swing.

The 74-year-old has a little jerky motion in his backswing ... but to his credit, the guy is still able to square up the clubface and drive it a mile.

"My man Mr DT," Cowan wrote along with the video. "Textbook."

Trump and most of those who have golfed with him recently have talked glowingly about his game ... with U.S. Senator Lindsey Graham saying over the summer that Donald shot a 74 in one of the rounds they played.

FYI -- a 74 is REALLY good ... some pros don't even hit that mark on a regular basis!

"He beat me like a drum!" Graham said at the time.

Then again, others who have played with Trump in the past have sworn he's a cheat on the course ... with Barack Obama recently saying of DT, "There’s sometimes problems with the scoring. And whether he’s keeping track of his strokes."