1. Points, Lines, and Planes
Lesson 1-1
Points, Lines, and Planes

2. Building Blocks of Geometry
Definition:
The three building blocks of geometry are points, lines, and planes.

3. Points B A C How to label: A * Use capital printed letters.
Definition: It is the most basic building block of geometry. It has no size. It has only location. B A
How to sketch a dot: C
How to label: A
* Use capital printed letters.
* Never label two points with
the same name (in the same sketch).

4. NEVER n Lines ? ? ? ? ? How to label: ? must have arrows at both ends
Definition: It is straight continuous arrangement of infinitely many points. It has infinite length but no thickness. It extends forever in two directions. n
NEVER ?
How to sketch: ?
must have arrows
at both ends ? ? ? ?
How to label:
Possible Names:
(Two methods)
1- small “script” letter
2- any two points on the line

5. Planes How to sketch: How to label: M P N * horizontal * vertical
Definition: It has length and width but no thickness. It is a flat surface that extends infinitely along its length and width.
horizontal “edges” M P
How to sketch: N
* horizontal
* vertical
* other
vertical
“edges”
How to label:
(Two methods)
1- capital “script” letter
2- any three points on the plane

6. Collinear Points Definition: Collinear points are points that lie
on the same line. (The line does not
have to be visible.)
collinear
non-collinear

7. Coplanar Definition: Points on the same plane Example:
Points D, E, and F are coplanar. D F E

8. Line Segment Definition:
Consists of two endpoints and all points between
How to sketch:
How to name:

9. Congruent Segments Definition: segments with equal lengths
( the symbol for congruent is = ) ~
Congruent segments can be marked with . . .
Numbers are equal. Objects are congruent.
AB: the distance from A to B ( a number )
AB: the segment AB ( an object )
Correct notation:
Incorrect notation:

10. Midpoint
Definition:
A point that divides a segment into two congruent segments.

11. Segment Bisector Definition:
Any object that divides a segment into two congruent parts which is the bisector of the segment.

12. Ray
Definition:
A ray begins at a point and extends infinitely in one direction.
How to sketch:
How to name:
( the symbol RA is read as “ray RA” )