# Triangles

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```					   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
angles.
   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
EQUILATERAL

congruent

ISOSCELES
   SCALENE – no sides congruent

SCALENE
Classifying Triangles by Their
Angles
   EQUIANGULAR – all angles are congruent

   ACUTE – all angles are acute
EQUIANGULAR

   RIGHT – one right angle        ACUTE

RIGHT

   OBTUSE – one obtuse angle
OBTUSE
Can You Classify the Different
Triangles in the Picture Below?

Classify the following triangles: AED, ABC, ACD, ACE
The Classifications…
   Triangle AED = Equilateral, Equiangular
   Triangle ABC = Equilateral, Equiangular
   Triangle ACD = Isosceles, Obtuse
   Triangle ACE = Scalene, Right

   So how did you do?
Question 1
   If a triangle has three      Answer:
unequal sides it is a            A) Scalene
______ triangle.
   A) Scalene
   B) Obtuse
   C) Isosceles
Question 2
   A triangle which has         Answer:
three equal angles is a          C) Equiangular
______ triangle.
   A) Acute
   B) Equilateral
   C) Equiangular
Question 3
   A triangle with (at least)      Answer:
two equal sides is a                B) Isosceles
______ triangle.
   A) Scalene
   B) Isosceles
   C) Congruent
Question 4
   Two triangles that are          C) Congruent
equal are called
______ triangles
   A) Acute
   B) Obtuse
   C) Congruent
Question 5
   A triangle with all three       Answer:
sides of equal length is a          A) Equilateral
______ triangle.
   A) Equilateral
   B) Right
   C) Equiangular
Question 6
   A triangle with an angle      Answer:
of 90° is a ______                B) Right
triangle.
   A) Acute
   B) Right
   C) Congruent
Question 7
   A triangle in which all      Answer:
three angles are less            B) Acute
than 90° is a ______
triangle.
   A) Right
   B) Acute
   C) Scalene
Question 8
   A triangle in which one       Answer:
of the angles is greater          A) Obtuse
than 90° is a ______
triangle.
   A) Obtuse
   B) Isosceles
   C) Acute
Question 9
   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
right angle.
   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
triangle.
World Problem 3
   In     ABC , < A = x, <B = x+45, and m<C
= 3x-15
   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.
Homework
   Pg. 267-269 # 4-18 even, 27,29,31

```
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