Classifying Triangles
Angle Sum Theorem
Triangle Inequality
Angle Pairs
Parallels and
Transversals
Transversals
100
A triangle with 3 equal sides and angles.
What is an equilateral triangle?
100
The sum of all the interior angles of a triangle.
What is 180o?
100
State the triangle inequality theorem.
What is "the sum of any two sides of a triangle must be greater than the third side"?
100
Identify the angle pair relationship.
What is complementary?
Work: 59 + 31 = 90
100
Lines m and l are congruent. If ∠6 = 118o, find the measure of ∠8.
What is 118o?
Work: Vertical angles are always congruent.
200
Classify the triangle by its angles.
What is an acute triangle?
200
Determine the missing angle.
What is 71o?
Work:
82 + 27 + x = 180
109 + x = 180
x = 180 - 109
x = 71
200
Determine if a triangle can be drawn with the sides 11, 12, and 17.
What is yes?
Work:
11 + 12 > 17
11 + 17 > 12
12 + 17 > 11
200
Identify the angle pair relationship.
What is supplementary?
Work: 146 + 34 = 180o
200
Lines m and n are parallel. If ∠3 = 42o, find the measure of ∠6.
What is 42o?
Work: Angles 3 and 6 are alternate interior angles, so they are congruent.
300
Classify the triangle by its sides.
What is an isosceles triangle?
300
Determine the missing angle.
What is 49o?
Work:
90 + 41 + x = 180
131 + x = 180
x = 180 - 131
x = 49
300
Determine if a triangle can be drawn with the sides 4, 8, and 15.
What is no?
Work:
4 + 8 < 15
300
Identify the angle pair relationship and solve for x.
What is complementary, x = 53o
Work:
x + 37 = 90
x = 90 - 37
x = 53
300
Lines k and i are parallel. If ∠4 = 37o, find the measure of ∠8.
What is 37o?
Work: Since k and i are parallel, corresponding angles are congruent so angles 4 and 8 are congruent.
400
Classify the triangle by its sides and angles.
What is scalene, obtuse triangle?
400
Use the angle sum rule to determine the value of x.
What is x = 12o?
Work:
90 + 2x + 1 +5x + 5 = 180
96 + 7x = 180
7x = 84
x = 12
400
If side AB is the longest side, the missing side (x) must be at least ___ .
What is 3?
Work: 8 plus the missing side must be greater than 10, so the missing side must be at least 3.
8 + 3 = 11
400
Identify the angle pair relationship and solve for x.
What is vertical angles, x = 49
Work:
126 = x + 77
126-77 = x
49 = x
400
The two horizontal lines below are parallel. If ∠CGE = 129, find the measure of ∠AHF.
What is 51?
Work: ∠CGE is supplementary to ∠EGD. This means ∠EGD = 180 - 129 = 51.
∠EGD and ∠AHF are alternate exterior angles, so they are congruent.
500
Classify triangle ABC by its sides, and identify the missing angle measure.
What is isosceles, x = 40?
Work: Isosceles angles have to sides of the same measure, and two angles of the same measure. So x must be the same as the other angle, which is 40o.
500
Use the angle sum rule to determine the value of x.
What is x = 14?
Work:
7x - 11 + 2x - 3 + 5x - 2 = 180
14x - 16 = 180
14x = 196
x = 14
500
Identify which set of numbers could NOT make a triangle.
(a)6,8,11
(b)9,12,19
(c)7,11,18
(d)5,6,7
What is (c)?
Work: 7 + 11 = 18
This is not greater than the other side (18) so these numbers cannot form a triangle
500
Identify the angle pair relationship and find the value of q.
What is supplementary, ∠DBC = 22o
Work:
(7q−46) + (3q+6) = 180
10q − 40 = 180
10q = 180 + 40
10q = 220
q = 22
500
Lines AB and CD are parallel. If ∠REB =40, find the measure of ∠EBC.
What is ∠EBC = 140o?