Transcript Geometry I Points, lines, segments, rays, and angles. Points A point

Geometry I
Points, lines, segments, rays, and
angles.
Points
• A point is an exact location, it can be
so very tiny that it can’t be seen.
• It can be located anywhere.
• When we name a point, we use a
capital letter.
A
T
W
X
G
Line Segment
• A line segment is a line that begins at
one point and ends at another.
• We name a line segment by naming
the two points it connects and then
placing a small line segment above
the points’ names. We read it as
B
segment RL, orRsegment LR.
RL
RU
R
UR
AB
A
LR
L
U
BA
Lines
• Lines go on and on in both
directions.
• We name a line by writing the names
of two points it crosses and placing a
small line symbol above them.
• It is read line EM or line ME
E
M
ME EM
Quick Review
• Line Segment…...
• Read as
segment RT or
segment TR
RT
TR
• Line…...
R
• Read as line
BY or lineYB BY
B
T
Y
YB
Rays
• Rays begin at a certain point and then
continue on and on.
• When we name a ray, we put it’s starting
point first, then the name of the other
point is crosses.
• We put a little ray sign above the name.
• It is read
ray RL.
L
R
RL
Match the following...
• Match the shapes with their names.
DW
• Read them.
D
WD
W
DW
W
D
WD
W
D
WD
Lines can be parallel running alongside one
another without ever
touching.
Lines can be intersecting crossing or meeting one
another at some point.
When lines intersect and
make four square corners,
they are
perpendicular.
Angles
• Angles are formed when two
lines intersect - meet or cross
one another.
• The point where the sides of the
angle meet is called the vertex.
The Vertex
• The vertex is the point where the two
sides of an
The angle ‘s
measurement
angle meet
is the
one
measurement
another.
of the space
between the
sides of the
angle.
Three Kinds of Angles
• You will be studying three kinds
of angles.
• They are named by their sizes.
• It’s important to remember their
names and sizes, it helps later
when deciding what their
measurement is on a half-circle
protractor.
Right Angles
• Right angles are 90° - no more, no
less.
They form square corners, this helps
to spot them.
90°
Acute Angles
• ACUTE - is a small angle,
less than 90°. Think of it
as “a cute little guy”!
Obtuse Angles
• Obtuse angles are larger than 90° think of them as “thick” or “fat”
angles, another word for fat is obese
- this might help you remember
obtuse.
Quick Review
• An ACUTE angle is less than 90°.
• A RIGHT angle is exactly 90°. It forms
a square corner.
• An OBTUSE angle is larger than 90°.
Measuring Angles
• We measure angles with a
protractor. There are two types the half
circle
protractor...
Measuring Angles
• The circular protractor - it
measures all the degrees in a full
circle.
• There are 360°
(degrees) in a
full circle.
Using the Protractor
• To measure the degrees in an angle,
we use the protractor.
• We place the vertex of the angle in
the place provided.
• We line up one side of the angle with
the zero line and then read the
measurement indicated by where the
other side of the angle is located on
the protractor.
• Let’s see how that works…………….
Line up one side of the angle with the zero line of the
protractor.
Read the numbers where the other side of the angle
points on the protractor..
65° acute angle
Put the vertex in the appropriate place
75° acute angle
Don’t get shook up if you put the angle
to the left or right side of the
protractor, just remember, ACUTE is
less than 90°, RIGHT is exactly 90°,
and OBTUSE is more than 90°. Read
the numbers accordingly.
106° obtuse angle
Are you confused about which number to
choose?
Remember - ACUTE angles are LESS than 90°, so
you pick the number that is less than the ninety.
ACUTE angles are smaller than square corners.
OBTUSE angles are LARGER than 90° so you
pick the number that is more than ninety.
OBTUSE angles are fatter or larger than square
corners.
RIGHT angles are exactly 90°.
When using a circular protractor,
line up one side of the angle with the
zero line. Remember to put the
vertex in the center.
Read the
Place the
vertex in
the center
area which
is marked.
60° acute
numbers
on the
protractor
that are
indicated
by the
second
side of the
angle.
Review
• Name the following angles and tell if
you would look for a number more or
less than 90°.
acute
less
right
obtuse
less
more
right
acute
obtuse
more
Read the Measurement
115° obtuse
Match the Terms
• Acute Angle
• Right Angle
Angle that is exactly 90°
Angle larger than 90°
• Obtuse Angle
Angle less than 90°
ANY
QUESTIONS?
•NOW
is the
time to ask questions or
for a review.