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SHAPES
GEOMETRY
TRIANGLE
TRIANGLE – 3 SIDED SHAPE
 TRI MEANS 3

TRIcycle (3 wheels)
TRIlogy (3 books in the series)
(3 Horns)
QUADRILATERAL


A quadrilateral is a polygon with 4 sides.
These are all quadrilaterals:
“QUAD” MEANS 4
Quadriceps –
4 muscles
Quadruplets (4 babies)
Quadrant – 4
sections
PENTAGON
•A pentagon is a 5-sided shape.
•“Pent” means 5
Pentagram – 5
pointed star
U.S. Pentagon in
Washington D.C.
HEXAGON
•A hexagon is a 6-sided shape
•“Hex” means 6
Hexagram –
6-pointed
star
(Ask Jacob)
HEX nut –
six sided nut
Hexapod – 6 feet
HEPTAGON
•A heptagon is a 7-sided figure
•“Hept” means 7
Heptathlon – 7 event competition
Heptadactyly– 7
fingers on 1 hand
OCTAGON
•An octagon is an 8 sided figure
•“Octa” means 8
Octogenarian – a person
who is in there 80’s
Octopus – 8 legs
Octamom!
NONAGON
•A nonagon is a 9-sided figure
•From the Latin word “nonus” and the
Greek word enneagonon, meaning 9
Enneagram – 9 personality types
DECAGON
•A decagon is a 10-sided shaped
•“Deca” means 10
Decimal – base 10 number system
Decade – 10 years
Decathalon – 10 track
and field events
LET’S REVIEW
CLASSIFYING QUADRILATERALS
Quadrilateral – 4 sides, 4 angles, a
type of polygon
Rectangle – opposite sides are
congruent; has 4 right angles
Square – 4 congruent sides; 4 right
angles
Parallelogram – opposite sides are
congruent and parallel
Rhombus – 4 congruent sides;
opposite sides are parallel
Trapezoid – only 1 pair of parallel
sides
LET’S CLASSIFY
Polygon
Quadrilateral
Trapezoid
Polygon
Quadrilateral
Parallelogram
LET’S CLASSIFY
Polygon
Quadrilateral
Parallelogram
Rhombus
Polygon
Quadrilateral
Parallelogram
Rhombus
Rectangle
Square!
TRIANGLES
A triangle has 3 sides
and 3 angles
TYPES OF TRIANGLES BASED ON HOW MANY SIDES AND ANGLES ARE EQUAL
An EQUILATERAL triangle has 3
equal sides and 3 equal angles
(always 60 degrees)
An ISOSCELES triangle has 2
equal sides and 2 equal angles
An SCALENE triangle has NO equal
sides and NO equal angles
TYPES OF TRIANGLES BASED ON TYPES OF ANGLES
An ACUTE triangle is a triangle
with ALL angles less than 90
degrees.
A RIGHT triangle is a triangle
with a 90 degree angle.
An OBTUSE triangle is a
triangle with an angle of more
than 90 degrees.
A TRIANGLE CAN HAVE TWO NAMES
isosceles right triangle
TRIANGLES
An equilateral triangle is always….
ACUTE
TRIANGLES
In a right triangle, one of the angles is a right angle—an
angle of 90 degrees. A right triangle may be isosceles
or scalene.
In an obtuse triangle, one angle is greater than a right
angle—it is more than 90 degrees. An obtuse triangle
may be isosceles or scalene.
In an acute triangle, all angles are less than right
angles—each one is less than 90 degrees. An acute
triangle may be equilateral, isosceles, or scalene.
YOUR TURN!
Draw each of the following:
1. Right isosceles triangle
2. Obtuse scalene triangle
3. An acute equilateral triangle
1. Right isosceles triangle
2. Obtuse
scalene triangle
3. Acute equilateral
triangles