2
1 Longest Sideand
Largest Angle
• Explore the relationship
between the longest side
and the largest angle in a
triangle.
• Investigate the
relationship between the
sum of any two sides and
the remaining side in a
triangle.
Investigate Relationships in
Triangles
Sum of Sides
5.
• Exterior AngleInequality Theorem
• Triangle Inequality Theorem
• Hinge Theorem and its converse
Triangle Inequalities
Illustrate Theorems
6.
Connect theorems intriangle inequalities to real-life settings.
Real-Life Connections
1 3
2
• Whyare
relationships
important in
understanding
structures?
Motivation
Learning
Targets
• Determine
relationships
between
angles and
sides of a
triangle.
• Apply
triangle
inequalities to
solve real-life
problems.
Essential
Question
Introduction (5 minutes)
• Present real-
world
structures
(e.g., bridges,
roofs, support
beams) and
discuss
stability
through
triangular
formations.
9.
• Protractor, ruler
Interaction(30 minutes)
Activity A: Investigate
Me!
• Directions: Use the figure
below to answer the
questions that follow. Write
your answer on a separate
sheet of paper.
• What is the included side in
B and C? in E and F?
∠ ∠ ∠ ∠
• What is the included angle in
and ? in and ?
𝐴𝐶̅̅̅̅ 𝐵𝐶̅̅̅ 𝐷𝐹̅̅̅̅ 𝐸𝐹̅̅̅̅
• What is the sum of the
interior angles of ABC?
∆
DEF?
∆
• If B E, and C F,
∠ ≅ ∠ ∠ ≅ ∠
Activity B: Materials
Needed
10.
2 3 5
14
Angle-Side
Relationshi
p Theorem
Discussion
• The sum of
the lengths of
any two sides
Converse
of Hinge
Theorem
or SSS
Inequality
Theorem
Triangle
Inequality
Theorem
• An exterior
angle is
• Larger
angle
Hinge
Theorem
or SAS
Inequality
Exterior
Angle
Inequality
Theorem
• If two sides
of one
4. Assessment
• Directions:Write your answer on
a separate sheet of paper.
Am I a Triangle?
• Directions: Determine if the
following lengths can form a
triangle. Use ( ) for yes and (X) for
∆
no.
• 1, 2, 3
• 17, 16, 9
• 9, 11, 18
• 4, 8, 11
• 5, 13, 6
Identify Me