A projection of the trefoil knot
The figure represents the possible projection on a plane of a trefoil knot; indeed, it could be also the projection of another knot. We can say that it is a trefoil knot only when we look at the diagram of the knot itself, in which the up-down position of the crossings is specified.
The image belongs to the sections...:
Images from the topology section (From the exhibitions of matematita)
Trefoil knot (Topology)