Let’s look at some vocabulary
terms before we start classifying figures.
Two-dimensional – having a width and a height
but flat like a piece of paper.
Polygon
Two-dimensions
Polygon – a two-dimensional shape made up
One-dimension
of straight lines that are closed. Three-dimensions
Polygons are either
This is a
or
.
polygon because ALL of its
sides and angles are
.
Congruent – having the same measure
Hash marks indicate sides with the same length.
Angle arcs indicate angles of the same measure.
This is an
polygon because
some of its sides and angles
are not congruent.
Here is a list of the most basic polygons:
Triangle
3-sided
Quadrilateral
Pentagon
Hexagon
Septagon
7-sided
Octagon
8-sided
4-sided
5-sided
6-sided
Nonagon
Decagon
9-sided
10-sided
Part 2
All triangles have:
 3 sides
 3 interior angles (that add up to 180°)
There are just a few basic ways
that we classify or name
triangles!
We classify or name triangles by their angles.
Acute Triangle
All angles < 90°
 All angles less than 90°
Right Triangle
 One 90° angle
“□” means 90°
One 90° angle
□
Obtuse Triangle
 One angle greater
than 90°
One angle > 90°
We also classify triangles by
their side lengths and angle measures.
Equilateral Triangle
 3 congruent sides
 All angles congruent
Isosceles Triangle
 2 congruent sides
 2 congruent angles
Scalene Triangle
 No congruent sides
 No congruent angles
Classify each triangle by ALL names that apply.
2.
____________________
Acute
1.
____________________
Isosceles
3.
□
____________________
Right
____________________
Isosceles
140°
____________________
Obtuse
____________________
Scalene
Part I
A main group of polygons are
the quadrilaterals.
All quadrilaterals have:
 4 sides
 4 interior angles (that add up to 360°)
We classify quadrilaterals based on whether or not
they have certain properties:
How many pairs of parallel sides it has
Parallel Line -Two lines on the same plane that will never cross. They
are always the same distance apart.
We classify quadrilaterals based on whether or not
they have certain properties:
The number of congruent sides it has
Congruent – having the same measure, indicated by
hash marks
These sides
are
congruent
These sides
are
congruent
We classify quadrilaterals based on whether or not
they have certain properties:
If it contain right angles
Right angles = 90 degrees, indicated by a square in the corner
Let’s classify quadrilaterals from those with the
fewest properties to those with the most properties.
Parallel sides? No
Congruent sides? No
Right angles? No
 4-sided polygon
 Quadrilateral with one
pair of parallel sides
Parallel sides? Yes, one pair
Congruent sides? Maybe one pair, but not necessarily
Right angles?
Maybe two, but not necessarily
 Quadrilateral with 2 pairs
of congruent adjacent sides
Parallel sides? No
Congruent sides?
Yes, adjacent
sides congruent
Right angles? No
Hash marks
indicate
congruency
 Opposite sides congruent
 Two pairs of parallel sides
Parallel sides?
Yes, 2 pairs
Congruent sides?
Yes, opposite
sides congruent
Right angles? No
Parallel sides?
Yes, 2 pairs
Congruent sides?
Yes, opposite
sides congruent
Right angles? Yes
 Opposite sides congruent
 Two pairs of parallel sides
 4 right angles
Parallel sides?
Yes, 2 pairs
Congruent sides?
Yes, all sides
congruent
Right angles? No
 All sides congruent
 Two pairs of parallel sides
Parallel sides?
Yes, 2 pairs
Congruent sides?
Yes, all sides
congruent
Right angles? Yes
 All sides congruent
 Two pairs of parallel sides
 4 right angles
Name each of the following polygons.
1.
2.
trapezoid
YIELD
Coffee
3. parallelogram
F
FA
Future Farmers
of America
6.
5.
4.
Work
Zone
pentagon
7.
World Cup
2014
ITALIA
kite
trapezoid