Engineer's Pentagon

There are several ways one can draw a regular pentagon using just a straight edge and a compass. However there is one way which is even though a regular pentagon but is not the correct one. In the sense not all angles are equal. This construction is a good approximation and used by engineers. Take a look at the picture I drew using kig and notice that all the sides are equal but not all the angles in fact there are three different types of angles where two each of same type.