Sorry for the late reply. My internet service has been down for a couple of days.
Just threw this sketch together to show what seems to be the shortest most direct way to use math to solve the "field miter" question to get an exact finished length.
In this example I used the exact dimensions required by the author of the question.This time though, because of time constraints, there is no explanation of the "why",only the "how". Remember, if you're using slips and drives,do your calculation one inch short of the finish (drivetodrive) measurement.
Also,this caveat...Duct width sizes can grow dramatically when doing field miter cuts of this type. A 12 wide duct,24 inches long,just like the one in the drawing example,but with a 10" offset,grows to 13 INCHES !! 😭 (LET'S KEEP OUR STANDARDS HIGH And do quality work !!👌👍👏
