Boy I creamed on another thread for mentioning this way to calculate angle. I was made fun of for my "fussy, made up, equation!" which I pointed out wasn't "MY" equation but simply "the Riflemans Rule". most on that thread seemed to like an "improved" version which is cos x drop and others yet for "Sierras rule". Well here it is on video.... The Riflemans Rule
http://www.longrangehunting.com/forums/f73/correcting-inclined-shots-riflemans-rule-89407/
http://www.longrangehunting.com/forums/f73/correcting-inclined-shots-riflemans-rule-89407/