Download Section 9.3 notes

Section 9.3 ~
Classifying Polygons
Pages 470 - 474
A polygon is a closed plane figure with at least
three sides. The sides meet only at their
endpoints.
A triangle is a polygon with three sides. You can classify
triangles by angle measures. You can also classify triangles
by side lengths. Tick marks are used to indicate congruent
sides of a figure.
Classifying a Triangle
Classify the triangle by its sides and
angles.
The triangle has two congruent sides and one right angle.
The triangle is an isosceles right triangle.
Judging by appearance, classify the triangle by its sides and angles.
a. scalene right triangle
b. isosceles right triangle
c. isosceles obtuse triangle
d. scalene acute triangle
Judging by appearance, classify the triangle by its sides and angles.
a. scalene right triangle
b. isosceles right triangle
c. isosceles obtuse triangle
d. scalene acute triangle
Judging by appearance, classify the triangle by its sides and angles.
a. scalene obtuse triangle
b. isosceles acute triangle
c. isosceles right triangle
d. scalene right triangle
You can also classify quadrilaterals by their sides and angles.
Classifying Quadrilaterals
Name the types of quadrilaterals that have both
pairs of opposite sides parallel.
All parallelograms have opposite
sides parallel. Parallelograms include
rectangles, rhombuses, and squares.
In later math courses, you will prove that a
parallelogram has opposite sides
congruent and opposite angles congruent.
Polygons are named using their vertices.
Start at one vertex and list them in
consecutive order.
A regular polygon has all sides congruent
and all angles congruent. Some regular
polygons are shown below.
Real-World
Problem Solving
A contractor is framing a regular octagonal gazebo. Write a formula for
the perimeter of the gazebo in terms of the length of a side. Evaluate
the formula for a side length of 7 ft.
To write a formula, let x = the length of
each side.
The perimeter of the regular octagon is
x + x + x + x + x + x + x + x.
Therefore the formula for the perimeter is
P = 8x.
For a side length of 7 ft, the
perimeter is 56 ft.
Check Understanding
Write a formula to find the perimeter of a regular hexagon.
a. P = 6 + x
b. P = 5x
c. P = 5 + x
d. P = 6x
Use the formula to find the perimeter if one side is 16 cm.
a. 80 cm
b. 21 cm
c. 96 cm
d. 22 cm
Homework
pages 473 - 474
#s 1-25, 32-35
–
–
–
–
draw diagrams AND
write problems and answers, EXCEPT for
word problems and multiple-choice
problems
SHOW ALL WORK!
failure to write problems and/or show work
will result in either receiving partial or no
credit