Edges and vertices 10 Schläfli symbols . Construction A regular decagon is constructible with a compass and straightedge.Complete steps 1 through 6 of constructing a pentagon.Extend a line from each corner of the pentagon through the center of the circle made in step 1 of constructing a pentagon to the opposite side of that same circle.The five corners of the pentagon constitute every other corner of the decagon. The remaining five corners of the decagon are those points where the li… (More on Decagon)