MJ2
Ch 10.5 - Quadrilaterals
Bellwork
 Draw the triangles and find the value
of x
1.
2.
x°
34°
56°
53°
x°
Assignment Review
Reminder:
 Your Triangle Poster is Due on _________
 I will add 5 points to your grade if your
poster is handed in on ___________
 Unfortunately, If the poster is not handed in
by ________ I will give you a zero (0) as I
do not accept late assignments!
Before we begin…
 Please take out your notebook and
get ready to work…
 For the past couple of days we have
been studying angles and triangles…
 Today we will look at quadrilaterals…
 Raise your hand if you know what a
quadrilateral is…
Quadrilaterals
 Correct…a quadrilateral is a closed
figure with 4 sides and 4 angles…
 Raise your hand if you can name
some examples…
Objective
 Students will classify and find the
missing angle measure of
quadrilaterals.
Classifying Quadrilaterals
 When classifying quadrilaterals you
use the name that best describes it…
 That means we all need to have the
same understanding of the
characteristics of each type of
quadrilateral
 Please copy the vocabulary on the
next slide…
Vocabulary
 Quadrilateral – any 4 sided, 4 angle figure
 Trapezoid – a quadrilateral with one pair
of parallel sides
 Parallelogram – a quadrilateral with
opposite sides parallel and opposite sides
congruent
 Rectangle – a parallelogram with 4 right
angles
 Square – a parallelogram with 4 right
angles and 4 congruent sides
 Rhombus – a parallelogram with 4
congruent sides
Comments
 When viewing pictures of quadrilaterals
there are 2 types symbols that you need to
be aware of
 The hash mark (/) means the sides are
congruent. If multiple sides are congruent
you will see 1 or 2 hash marks
 The arrow () indicates that the sides are
parallel. If multiple sides are parallel you
will see 1 or 2 arrows.
 Lets look at some examples…
Examples
Square: 4 right angles & 4
congruent sides
Trapezoid – 1 set of parallel
sides
Missing Angle Measurements
 All the angles in any quadrilateral
equal 360° .
 To find the missing measure use the
same process as finding the angles of
a triangle.
1. Add up the given angles and subtract
from 360° .
2. Lets look at an example…
Example
Before you begin…look
at angle x.
Will it be >90°, <90°,
or =90° ? Why?
Raise your hand if you
know the answer..
108°
55°
x°
59°
Example
 Correct…because x is an
obtuse angle it will be
greater than 90°
 The reason you look at
that is to make sure that
your answer is
reasonable…so if you get
an answer less than or
equal to 90°, you have to
question it!
108°
55°
x°
59°
Example
 To find the missing measure
add up the angles and
55°
subtract from 360°.
360-(108+55+59)=x
360 – 222 = x
138 = x
Therefore, x = 138°
and your answer is reasonable!
108°
x°
59°
Your Turn
 In the notes section of your notebook
draw the figure and solve for x
x°
113°
Summary
 In the notes section of your notebook
summarize the key concepts covered
in today’s lesson
 Today we discussed
 The types of quadrilaterals – you will see
this on a test!
 How to find the missing angle of a
quadrilateral!
Assignment
 Quadrilateral Concept Map
 Follow the directions on the sheet!