Goal – To classify
triangles according to
angles and sides.
Different Types of Triangles
There are several different types of triangles.
You can classify a triangle by its sides and its
There are THREE different classifications for
triangles based on their sides.
There are FOUR different classifications for
triangles based on their angles.
Classifying Triangles by Their Sides
EQUILATERAL – 3 congruent sides
ISOSCELES – at least two sides
SCALENE – no sides congruent
Classifying Triangles by Their
EQUIANGULAR – all angles are congruent
ACUTE – all angles are acute
RIGHT – one right angle ACUTE
OBTUSE – one obtuse angle
Can You Classify the Different
Triangles in the Picture Below?
Classify the following triangles: AED, ABC, ACD, ACE
Triangle AED = Equilateral, Equiangular
Triangle ABC = Equilateral, Equiangular
Triangle ACD = Isosceles, Obtuse
Triangle ACE = Scalene, Right
So how did you do?
If a triangle has three Answer:
unequal sides it is a A) Scalene
A triangle which has Answer:
three equal angles is a C) Equiangular
A triangle with (at least) Answer:
two equal sides is a B) Isosceles
Two triangles that are C) Congruent
equal are called
A triangle with all three Answer:
sides of equal length is a A) Equilateral
A triangle with an angle Answer:
of 90° is a ______ B) Right
A triangle in which all Answer:
three angles are less B) Acute
than 90° is a ______
A triangle in which one Answer:
of the angles is greater A) Obtuse
than 90° is a ______
What is the Hypotenuse Answer:
of a right triangle? B) The side opposite the
A) The smallest angle. right angle.
B) The side opposite the
C) The right angle.
Word Problem 1
In triangle ABC the measure of <B is twice the
measure of <A, and the measure of <C is 3
times the measure of <A. Find the number of
degrees in each angle of the triangle.
Word Problem 2
The measure of each base angle of an isosceles
triangle is 7 times the measure of the vertex
angle. Find the measure of each angle of the
World Problem 3
In ABC , < A = x, <B = x+45, and m<C
Find the measures of the three angles
What kind of triangle is ABC?
Writing in Math
Taylor said that if the sum of the measures of two
angles of a triangle is equal to the measure of the
third angle, the triangle is a right triangle. Prove or
disprove Taylor’s statement.
Pg. 267-269 # 4-18 even, 27,29,31