Triangles--ah yes, what I do is make the triangles a bit larger than needed then trim to exact size. I'm talking about sewing two triangles together to make a square. I cut two squares about 1/4" larger than needed, draw the line down the center, put them together and sew scant 1/4 on each side of that line. Cut, press then square them to the exact size I need. I know it takes a bit more time, but they sure are accurate.