Name of Teacher: ELEM, MAYBELLE TORRES
Date: May 05, 2023
Learning Area: MATHEMATICS
Grade/Level/Section: Grade 8
Time:9:45-10:45am
Competencies: Illustrates theorems on triangle inequalities-M8GEIVa-1
iPlan No.
Duration:
4
1 Hour
Key
Concepts
to The exterior angle theorem states that the measure of an exterior angle is equal to the
Understand
sum of the measures of the two opposite(remote) interior angles of the triangle.
Subject Matter: Illustrating Exterior Angle and Remote Interior Angles Inequality Theorem on Triangle Inequalities
Learning Objectives
Recall triangle inequality theorems.
Illustrates the exterior angle and remote interior angles inequality theorem
Skills
on triangle inequalities ;and
Find the measure of exterior and interior angle.
Participate in group activity and cite ways to promote equality and prevent
Attitudes
inequalities.
Grade 8 Learner’s Module, Multimedia presentation, Cartolina, Marker, Activity Sheet
Resources Needed
Elements of the Plan
Methodology
Preparation
Knowledge
1.
2.
3.
4.
Prayer
Greetings
Checking of attendance
Classroom management (setting of classroom rules)
Motivation
Cabbage Relay
1. An improvised cabbage will be relayed to the class while the music plays.
2. The student who holds the cabbage when the music stops has to peel one strip from the
cabbage, and then he or she will answer the question within it.
The questions are...
First Strip
State whether it is true or false(The triangle inequality theorem states that "The sum of any two
sides of a triangle is less than its third side." )
Second Strip
In your own understanding, what does Triangle Inequality Theorem 1 state?
Third Strip
Fill Me! Triangle Inequality Theorem 2 states that “ if one angle of a triangle is _____ than the second
angle, then the side opposite the larger angle is _____ than the side opposite the second angle.”
Fourth Strip
What theorem states that “ the sum of the lengths of any two side is greater than the length of the
third side.”
Activity
There will be Activity Card #1, #2,#3 and #4 that will be presented to the class.
The class will be divided into four groups and each group will choose a leader to pick 1 activity card.
Each group will be given cartolina and marker to answer the question/s inside the activity card.
They will be given 10 minutes to do their chosen activity card. Finish or not finish, they have to
present there work in front.
Criteria
Accuracy
Organization
Content Knowledge
Score
15
15
10
Delivery
Total
10
50
Activity Card #1
Directions:
Illustrate an equilateral triangle and name it △ABD.
In segment AD, extend it to N.
Label the exterior angle shown in your illustration.
Activity Card #2
Directions:
Illustrate an equilateral triangle and name it △ABD.
In segment AD, extend it to N.
Label the remote interior angle shown in your illustration.
Activity Card #3
Questions:
Given ∠B=50°, what is the measure of ∠A?
What are the remote interior angles?
B
50°
A
D
N
Activity Card #4
Questions:
If ∠1=50°, ∠2=50°, what is the measure of ∠4?
B
What do you call ∠4?
1
2
A
4
D
N
Analysis
1.
2.
3.
4.
How did you find the activity?
Do you have difficulties in answering your activity? Why?
Are all the members of the group participated?
For group 1 & 2, what are the things did you consider to identify exterior angle and
interior angles?
5. For Group 3 & 4, how did you find the measure of the angles?
Abstraction Exterior and Remote Interior Angle Inequality Theorem
For
any triangle, the measure of an exterior angle is equal to the sum of
its two remote interior angles.
B
EXTERIOR ANGLE
A
.
D
N
Exterior angle is an angle that forms a
linear pair with one of the angles of
the triangle.
Remote interior angles of a triangle
are the angles that do not form a linear
pair with the exterior angle.
B
1
2
3
A
.
4
D
N
m∠4=m∠1+m∠2
> m∠1
m∠4 > m∠2
m∠4
Example:
1.
Find the value of m∠DBC by Exterior Angle Inequality Theorem.
A
B
C
49°
68°
D
Solution:
∠A+∠D=∠DBC
49°+68°=∠DBC
117°=∠DBC
∠DBC=117°
Application
(BOARD WORK)
Find the value of x.
60°
80°
18°
x 112°
x
x=
Assessment
x=____
Directions: Find the measurement of each missing angle in the triangles below. Remember, the
Exterior Angles Theorem states that the exterior angle is congruent to the sum of the two nonadjacent angles.
1.
2.
3.
Assignment
50°
4.
5.
Directions: In your notebook, copy and answer the problem below.
Find the value of x.
A
B
5x+10
58°
D
11x+2
E
References:
Grade 8 Mathematics Learner’s Module.
Prepared by: MAYBELLE T. ELEM
Student Teacher
Checked by: ROQUESA R. PAULIN
Mentor