Ok guys remember there are no stupid questions, only old guys that have forgot their geometry. I am cutting tubing for my frame. I know if I want to join two pieces of square tubing and make it match for a 90 then I divide by two and cut two 45's like a picture frame, but I get dumb after that. Here is a picture of one of the joints I am cutting. The two pieces are cut at 30 degrees on the chop saw. The inside angle is around 135 degrees, as you can see I need to cut it different to close up the gap and make it match. What's the rule for this or a good web site, with pictures.