It appears it is not possible to have an manual area or linear take off calculate slopes or angles? I have looked around but was unable to find a solution. Has anyone figured out how to do this or even a work around?
This is not currently possible in Quantity Takeoff. I’ve logged an enhancement request in this regard with our development group.
As described on "Inputs allowed in forumas" page in the help, you are able to calculate angles using inputs such as asin:
However, what you are describing, it sounds like you are hoping to measure/markup the sheet or report the angle value which isn't possible.