ORIGINAL: dohcrxl
Arthur P, your mention of the Pythagorean Theorum leads me to believe that it doesn't matter how high you are in the tree, you must always shoot at the deer depending on how far it is from the base of the tree.
BINGO!!!! We have a winner!! DING DING DING!!! Yes, sorry my explanation was a little confusing, but this is whatI was trying to tell you. Your arrow drops because of gravity. Gravity pulls down on the arrow over the horizontal distance that it travels. The farther it goes the more it is pulled down. SO to answer how to know where to aim, you must figure out the horizontal distance between you and the intended target. How high up you are doesn't matter. You must know the distance from the base of the tree to the deer. That is why when I put up a stand, I measure the distance from the base of the tree to where I think the deer will be. Then when the deer is there I already know the horizontal distance to it, and I can center punch his lungs