: DRAWING AND ITS UTILITY
The focal point of a circle is its center, and is called the focus
. But an ellipse has two focal points, called foci
, represented by F, F in Fig. 148, and by B, B in Fig. 149.
A produced line
is one which extends out beyond the marking point. Thus in Fig. 148 that part of the line K between F and G represents the produced portion of line K.