Each of the images below has a link to a step-by-step geogebra applet through which it is possible to move forwards and backwards in the construction, or watch how the construction is solved in a short animation. The blue “circular” points in some applets are movable.
These applets are gathered in this this GeoGebra book.
regular decagon inscribed in a circle
regular decagram inscribed in a circle
geometry addiction 