it doesn't matter if you are 100 feet up a tree. if a deer has a horizontal distance of 20 yards, you use your 20 pin. if the deer is 1 yard away from the bottom of your tree, you use whatever pin equates with you hitting a bulls-eye from 1 yard away - which for me would be my 70 yard pin.

the pythagorean theorem is of absloutely no significance - unless you're 30 ft up a tree and you use your range finder to see how far a trail is. say the deer trail is 60 ft from your position in the tree. that ='s the hypotenuse of the triangle. you would then use that (c squared) and your known height up the tree (b squared) to determine your horizontal distance from the trail (a squared). you would then compute (a squared) = ( c squared) - (b squared). then you would take the square root of (a squared) and use that distance for your pin. this gets into physics, but the only important thing is the horizontal distance from your objective. neither vertical nor diagonal distance has anything to do with it unless you use them to help you determine horizontal distance.