Marking two points A and B fixes a straight line through A and B. The line's direction vector is (B-A).
Marking a line g and a point A defines a straight line through A parallel to g. The line's direction is the direction of g.
Marking a line g and a point A yields a straight line through A perpendicular to g. The line's direction is equivalent to the perpendicular vector (4.3.5) of g.
The line bisector of a line segment is stated by a segment s or two points A and B. The line's direction is equivalent to the perpendicular vector (4.3.5) of the segment s resp. AB.
Angular bisectors can be defined in two ways.
The direction vectors of all angular bisectors have length 1.
The tangents to a conic can be produced in two ways:
Marking a point A and a function f produces the tangent line to f in x=x(A).
This mode creates the polar resp. diameter line of a conic section: