Geometry Notes 1.3 Points, Lines and Planes Mr. Belanger

Point Point – dot with no measurable size (doesn’t affect area or length)

Space Space – set of all points in 3-D (think air particles)

Line Line – straight connection of two points that goes forever in opposite directions (should have arrows on both ends)

Collinear Collinear – points that lie on the same line ( O is point at intersection) Points COD are collinear. Points AOB are collinear. Name three that are not collinear. COB, DAB

Plane Plane – flat 2-D space that goes on forever. (think wall or white board) Coplanar – two or more points on the same plane.

Undefined Terms Point, line, plane are all undefined terms. Meaning they are defined by real words, but their concepts cannot be taken literally and are just accepted as fact. Like a point has no size, even though you can see it A line and a plane have no thickness, even though you can see it

Postulate (axiom) Postulate (axiom) is an accepted statement of fact 1-1: through any two points there is only one line 1-2: if two lines intersect, they cross at one point 1-3: if two planes intersect they form a line 1-4: through any three non-collinear points there is only one plane