lesson 2 undefined terms. in geometry, there are 3 undefined terms: points, lines, and planes. we...
Post on 20-Jan-2018
248 Views
Preview:
DESCRIPTION
TRANSCRIPT
LESSON 2
UNDEFINED TERMS
In Geometry, there are 3 undefined terms:
points, lines, and planes. We can give descriptions of these three terms.
We also use these terms to help us write definitions of other terms such as segment, or ray
WHY THESE TERMS CALLED WHY THESE TERMS CALLED UNDEFINED? UNDEFINED?
It is because they can It is because they can only be defined only be defined circularlycircularly which means in terms of which means in terms of each other or in terms of each other or in terms of themselvesthemselves..
POINTA point is usually represented by a dot on a piece of paper .It is so small that it can never be measured because it has no dimensions at all.
- It shows location. - It is named by one capital letter.
A B C
A, B, and C are COLLINEAR POINTS
COLLINEAR POINTS- Points that lie on the same line.NONCOLLINEAR POINTS- Points that do not lie on the same line.
Examples COLLINEAR POINTS
- B, A, L, K- S, M, K- Q, M, ? - T, ? , D S
MQ
BD H
T
KLA
Examples NONCOLLINEAR POINTS
- B, A, M, K- D, M, K- Q, M, ? - T, ? , D S
MQ
BD H
T
KLA
LINESLINES-A line is always straight A line is always straight and travels forever and travels forever (INFINITE) in two (INFINITE) in two directions.directions.-has no width BUT IT HAS has no width BUT IT HAS length( which is infinite).length( which is infinite).
ILLUSTRATION
A B CThe opposite arrow indicates that it extends indefinitely in opposite direction.
Lines can be named in 2 ways:1. by its endpoints. For example, in the figure,
A B CLine AB or AB. Or Line BA or BA
Line AC or AC. Or Line CA or CA
2. Lines are also named with lowercase letters or a single lower case letter
A B CThe line above can be named also as line m instead of line AB or line AC.
m
A B D
WHAT HAPPEN IF YOU CUT THE LINE SHOWN
BELOW AT POINT B and C? WHAT ARE THE NEW
FIGURES FORMED?
C
SUBSETS OF A LINE
A B
DCA B
C DB C
RAY RAYSEGMENT
SUBSETS OF A LINE
B
Definition :-is a straight line segment which is part of the straight line between two points .-The points on each side of the line segment are referred to as the end points
CSEGMENT
SUBSETS OF A LINE
B
Segment is named by its endpoint.Segment BC or segment CB.
In symbol, BC or CB
CSEGMENT
SUBSETS OF A LINE
A
Definition :-A ray is the part of the line which consists of the given point and the set of all points on one side of the end point.
-The ENDPOINT is the starting point and the ARROW determine the direction of the ray.
B
SUBSETS OF A LINE
A
In writing,ray BA but not ray AB.ray CD but not ray DC.
DB C
RAY RAY
SUBSETS OF A LINE
A
In symbols,BA (reads as ray BA)CD (reads as ray CD)
DB C
RAY RAY
PLANEA plane is often represented by a FLAT SURFACE. These 'plane' surfaces are used to connect any two or more points on a straight line.
THE FLOOR
THE WALL AND THE CEILING
PLANEIn naming,-Named by 3 distinct points which are not collinear.-For example, plane BDC.
D
BC
β
PLANEor-Single greek alphabet.-For example, Plane β
β
PLANE-A plane has no thickness and edges.- has length and width.
ASSESSMENT
top related