Download Welcome to Geometry. Today, we`re going to the library for a bit

Your warm up is
on the back
table, on blue
paper.
Welcome to Geometry.
Please do the following warm up:
Match the shape with it’s name
A
C
____
Rhombus
M
____
Cube
K
____
Pentagon
I
____
Regular pentagon
N
____
Hexagon
L
____
Regular hexagon
J
____
Square
F
____
Isosceles triangle
____
A
Obtuse triangle
____
Right triangle
B
____
Acute triangle
G
____
Equilateral triangle
E
____
Trapezoid
D
____
Rectangle
O
____
Cylinder
H
B
D
C
E
G
H
F
I
J
L
K
All sides are
congruent. All
angle measures
are equal.
All sides are
congruent. All
angle
measures are
equal.
N
M
O
Rigid Transformations
• Transformations that do not change shape
or size.
• Pre-image is the original shape
• Image is the shape that undergoes a
transformation
NOTATION
• For instance a triangle would be called
ABC. This is the pre-image.
• The image of triangle ABC is called A’B’C’
(said, “A prime, B prime, C prime”). This is
so we can tell the difference between the 2
identical figures.
Transformations
• There are 3 types of rigid transformations:
– Translation – shapes slide
– Rotation – shapes turn
– Reflection – shapes flip
Translation
• Shapes slide
– Every point of a figure moves in a straight
line, all points move the same distance and
same direction.
A
A’
Rotation
• Rotations turn
– Every point of a figure moves around a given
point called the center of rotation.
B
B’
A
A’
Notice the center of rotation can be inside or outside of the shape
Reflection
• Reflections flip.
– In a reflection, a line plays the role of a mirror.
Every point in a figure is ‘flipped’ across the
line.
A’
A
Summary
• What is the movement of a rotation?
– What does is ‘turn’ around?
• What is the movement of a translation?
– What does it ‘slide’ on?
• What is the movement of a reflection?
– What does it ‘flip’ over?
• When can the pre-image and the image be a
different size?
• How do you notate the image and the preimage? (use point A for example)
Quick review
Obtuse triangle – contains one obtuse angle
Acute triangle – all angles 90°
Right triangle – contains one 90° angle
Equilateral – all sides have the same
measure
Equiangular – all angles are congruent
Equilateral triangle – all SIDES have the
same measure AND all angles are
congruent.
New vocabulary
Midpoint – is the point in the middle of a line
segment. Since it is in the middle, the
sides on either side of the midpoint are
congruent.
midpoint
Line segment
Rotational symmetry – a shape has
rotational symmetry if you can rotate it and
it ‘lands on itself’. Rotational symmetry is
measured in degrees. An object does not
have rotational symmetry at 0° and 360°.
Think of H.
Does H have rotational symmetry?
(yes)
At how many degrees?
(180°)
Think of E.
Does E have rotational symmetry?
(no)
At how many degrees?
(only at 0° and 360°, so it doesn’t
count)
Reflectional symmetry – a shape has
reflectional symmetry if it has a line of
symmetry
Think of H.
Does H have reflectional symmetry?
(yes)
Where is the line of symmetry?
(there are two; one vertical and one
horizontal)
Think of F.
Does F have reflectional symmetry?
(no – it does not have a line of
symmetry)
Hop in the Way-Back Machine
SLOPES OF LINES
y = mx + b
m is the slope
b is the y-intercept
How can you tell if two lines are
parallel?
slopes are the same
How can you tell if two lines are
perpendicular?
slopes are the negative
reciprocal of each other
How can you tell if two lines are neither
parallel or perpendicular?
The slopes have no relationship.
Your assignment
pg 42:
82, 83ab, 84 – 86
pg 48:
92 – 96 (not 94d)