i Mitre box
Professional tradesmen use iMitrebox to calculate compound mitres..
As an ex carpenter. I know that one of the most difficult things to do, on site, is calculate the compound angles needed to cut accurate joints in cornice / coving, or any mouldings that sit at an angle to the surface.
I developed iMiterbox to accurately give you the angles you need to set-up your compound miter saw to handle these cuts