Mike,Bryan, don't you mean Drop*[1-COS(@)]
If you would have 100" drop level, but shooting at 30deg,, 100*COS(30deg) would appear to be 15.4"
Where 100"*[1-COS(30)] would be 84.6" (I believe this).
Why not both...what? Do you mean to have a tool that gives both readings?Why not both?