Hello everyone, I am relatively new to all of this but am trying to focus on the roofing angles. What I would like to do is be able to work out my own roofing angles, using trig, without having to rely on the pages by Joe Bartok and book by Sim Ayers, speed squares or construction master calculators. For example, I know that tanHip=tanmainpitch*sinplanangle . I only know that because it has been worked out and written down already. As many hours as I have spent looking at the drawings with that formula, and using my pretty basic trig and geometry knowledge I cannot get my head around this for myself. Any help would be much appreciated