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Jose M Bravo Jr.
Chapter 11.1
Introduction to Basic Geometry
Basic Geometric Concepts
Point, Line, Line Segment
Definitions
A point is an exact location in space. A point has no dimensions.
A line is a collection of points along a straight path that extends endlessly in both
directions.
A
B
A line segment is a part of a line having two endpoints. A line segment has only
one dimension-its length. (Example AB on the figure above.)
Ray, Angle, and Plane
A ray is a part of a line having only one endpoint.
An angle consists of two rays that have a common
endpoint called the vertex of the angle.
C
Vertex
B
A
A plane is a flat surface that extends endlessly in all
directions.
Definitions
A straight angle is 180
Example
A
A right is an angle
That measures 90
B
C
D
F
E
X
An acute angle is less than 90
Y
Z
An obtuse angle is more than
90 and less than 180
C
E
D
Angles are measured in
degrees ( )
Angles are classified according
to their measures.
Complementary and
Supplementary Angles
Complementary angles are two angles whose
sum is 90.
25
A
65
B
Supplementary angles are two angles whose sum is 180
140
40
C
D
Intersecting lines, Parallel lines,
Perpendicular lines
Intersecting lines are two lines that meet.
B
DD
A
C
E
Parallel lines are two lines in the same plane that do not
intersect.
E
F
G
H
Perpendicular lines are two lines that intersect to form right
angles.
R
S
P
T
Symbol for right angle
Q
Vertical Angles
Vertical angles
are two equal angles formed
by two intersecting lines.
B
120
D
A
60
60
120
C
E