Angle Degree Indicator

You aim at your target, look at what number the red line on the indicator is next to, you then multiply that number by the distance of your target and that gives your actual distance. I.e. line is at .98 on the indicator. Range finder distance was 300. Mult 300*.98=294 actual distance.
 
You buy it, install it on your rifle and when you shoot is spins round and round. LOL.

In reality, unless you are doing a lot of angle shooting you might want to put the money into a Laser Range finder. I do have an ACI and besides looking cool I really have not had a need to use it. The one advantage of the ACI unit would be on a goat hunt or shooting elk at steep inclines. You do not need to hold anything against your scope, it is right there.

If you do decide to get one, Steve has them for a decent price. Triad Tactical, Inc.*::*Badger Ordnance*::*Badger ACI assembly
 
I think you gave the math for the ACI or Angle COSINE indicator, NOT the Angle Degree Indicator. The Angle Degree Indicator give values like 5,10,15,20,25 etc

HireHeroes_JB >> If you choose, the ADI because you want to know the angle you might want a multiplier card or Ti scientific calculator too so it will give you a cosine calculation (Degrees X COS button)Distance = gravity range. OR just get the ACI :)

Diver beat me to it. There is a difference between an Angle Cosine Indicator versus a Angle Degree Indicator.