I think you're thinking of the age old Pythagorum Theorum (A2+B2=C2) Let's take this example.....

Level Ground ---- 20 yards = 20 yards.

20ft. up in air aiming down at 20 yards (60 ft.)

20x20=400
60x60=3600
(a)400 + (b)3600 = (c)4000

Square root of 4000 = 63.24555
Translate/divide out into yards (3' to a yard): 63.24555 / 3 = 21.08

Long story short: 20 yard pin on level ground = 20 yards. 20 yard pin @ 20' = 21.08 yards. Therefore, with the age old Pythagorum Theorum, you'll hit just a hair high at 20 feet up @ 20 yards.

Thus concludes our mathmatical lesson.....

Butch A.