Download PPT 1.2 Finding Angles

1.2 FINDING ANGLES
Geometry
DO NOW:
Clock A
Clock B
IS THE ANGLE BETWEEN THE HOUR AND
MINUTE HAND THE SAME ON BOTH
CLOCKS? EXPLAIN YOUR ANSWER AND
THEN EXPLAIN HOW YOU WOULD PROVE IT.
Protractor
A device used to measure angles.
ARE THESE PROTRACTOS LINED UP
CORRECTLY?
No!! The angles must be lined up properly.
Look for the upside down ‘T’ in
the middle of the straight line on
your protractor.
In this protractor look
for the hole in the
center.
These spots need to be exactly on the
vertex of your angle.
We also need to remember to
line up the base
One side of the angle must be lined up
with the base of the protractor.
It doesn’t matter which side.
WHAT IS THE ANGLE MEASURE?
The side of the angle passes over 2 measurements:
145° and 35°. Which one is correct??
This angle measures 35°.
Now on your own, draw any angle you wish and
measure it!
CAN YOU DRAW ME A 60 DEGREE ANGLE?
Now can you
draw me a
bisecting ray of
that angle we
just made?
What do we notice?
What do you see??
Pool Table Problems
The incoming angle equals the outgoing angle.
What do you notice
about the outgoing and
incoming angles?
INDIVIDUALLY: STEP 1 AND STEP 2
Then we will share with our group.
Pool Table Problems
If I was to hit the white ball on the path given,
which letter would it hit after I hit the cushion
wall?
Pool Table Problems
Which point should I hit I could hit the 8-ball
exactly? W? X? or Y?
Pool Table Problems - Notes
Where do we aim on the
bottom cushion so white
hits blue?
Where do we aim on the
top cushion so white
hits blue?
Where do we aim on the
left cushion so white
hits blue?
Where do we aim on the left
cushion so white hits the
bottom cushion and then
hits blue?
Full Revolution
A revolution is an angle that equals exactly 360º.
NAMING ANGLES
An angle is made of two rays.
We label the angle with three upper
case letters.
Y is called
the Vertex
Y
Naming the Angle
 XYZ
 ZYX
Y
X
Z
Use a single letter to name the angle.
B
A
B
C
Use a single letter to name the angle.
Q
Q
P
NAMING ANGLES
R
Use a single letter to name the angle.
G
E
G
F
Use three letters to name the angle.
LNM
L
N
M
Use three letters to name the angle.
S
RST
R
NAMING ANGLES
T
Use three letters to name the angle.
EGF
E
G
F
Reflex Angle
A reflex angle is greater than 180º and
less than 360º.
It represents the largest amount of rotation.
Angle Bisector
line or line segment
that divides the
angle into two equal
parts (marked by slash
marks).
.
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