Figure 1.2
Figure 1.2 shows two lines l and m . Line l is such that it passes through A, B and C. Hence points A B and C are collinear. In the case of points P, Q and R there can be no single line containing all three of them hence they are called nonlinear.
Similarly points and lines which lie in the same plane are called coplanar otherwise they are called noncoplanar.
Axiom : A plane containing a line and a
point outside it or by using the definition of a line, a plane can
be said to contain three noncollinear points. Conversely, through
any three non collinear points there can be one and only one plane
(figure 1.3).
Axiom : If two lines intersect, exactly
one plane passes through both of them (figure1.4).
Axiom : If two planes intersect their intersection
is exactly one line (figure 1.5).
Figure 1.3
Lines A, B and C are contained in the same plane P or A, B and C are three noncollinear points through which one plain P can pass.
1.4
Plane Q contains intersecting lines l and m .
Figure 1.5
Planes P and Q intersect and their intersection is line l .
