Download Triangles

Warm Up
February 17, 2011
Complete your Fantastic
Four and grab two colored
pencils from the back table.
Objective:
• Today I will be
able to classify
different types of
triangles.
Classifying
Triangles
The sum of the
angle measures
of EVERY
triangle is 180°.
180°
Every triangle can
be classified by its
angles and by its
sides.
Classifying
Triangles by
Angles
•If EVERY angle
it
is less than
90°,
is an
ACUTE
Triangle.
•If the measure of ONE
angle is more than 90°
one is fat
it’s an OBTUSE triangle.
•If ONE angle
measures 90°it
is a RIGHT
triangle.
Classifying
Triangles by
Sides
•No sides the
same
•If none of the
sides have the
same length,
it is SCALENE.
•If
at least
two sides
measure the same,
it is an ISOSCELES
triangle.
Try to think of an isosceles
triangle as a person.
The arms would be attached
on the congruent sides.
The point shared by the
congruent sides is the head.
The two other points
represent the feet.
The
angles
by the “feet”
are always congruent.
Try to figure
out which
angles are
equal.
Be careful, your
triangle might
be “tired”.
•If the measure
of EACH
side is
equal,
it is…
all
the
sides equal
EQUILATERAL.
All equilateral
triangles are also
equiangular…
•If the measure of EACH
angle is
equal, it is
all
the
same
Can a triangle be
right and isosceles?
What
is the
measure
of the other
1 two angles? 2
A.
45°
45°
B.
60°
60°
60°
C.
65°
65°
50°
D.
17°
135°
28°
E.
65°
79°
36°
F.
71°
68°
41°
G.
100°
25°
55°
Classify Cut and Paste
• Start with the color to
classify the Sides
•Then cut out and
classify angles.