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Math Direct Instruction Lesson Plan
General Information
Lesson Title: Triangle Inequality Theorem with Geogebra
Subject(s): Geometry
Grade/Level/Setting: 10th grade
Prerequisite Skills/Prior Knowledge:
What do your students already know or what do they need to know about the selected topic to successfully
participate in the lesson?
Students already know:
• How to upload and submit assignments on google classroom.
• Triangles are three sided 2-D shapes
• Triangles are polygons and must be closed
• Polygon postulates and theorems for nonspecific shapes
Standards and Objectives
State/National Academic Standard(s):
G.GF.8: Prove and apply theorems about triangles including:
• Angle-Sum Theorem,
• Exterior Angle Theorem,
• Isosceles Triangle Theorem and its converse,
• Midsegment Theorem,
• Proportionality Theorem,
• Inequality Theorem and its converse, and
• Geometric Mean Theorem.
(Arkansas Division of Elementary and Secondary Education, 2023)
Learning Objective(s):
Identify what students will accomplish by the end of the lesson; needs to align with the state or Common Core State
Standards and needs to be measurable (condition, behavior, and criterion).
Given instruction on Triangle Inequality Theorem, Students will use Geogebra to create line segments of
different lengths given by the teacher to prove the theorem by connecting the two side lengths that
have a sum greater than the third side. Students should get an 8 out of 10 on the accompanying rubric
for mastery.
Materials Technology
, What materials will the teacher and the students need in How will you use technology to enhance teaching and
order to complete the lesson? learning? (Optional: Use the SAMR model to explain the
technology integration strategies you plan to use.)
Overhead projection/TV screen for modeling
Students will use the Geogebra software to
Computers with WIFI connection manipulate segments in order to connect or not
connect the three to make a triangle. This meets
Exit Ticket Worksheet the modification level of the SAMR model as
students are analyzing and evaluating segment
Pencil
lengths in order to prove the Inequality Theorem.
Language Demands
Specific ways that academic language (vocabulary, functions, discourse, syntax) is used by students to participate
in learning tasks through reading, writing, listening, and/or speaking to demonstrate their understanding.
Language Function(s):
The content and language focus of the learning task represented by the active verbs within the learning outcomes.
• Students will discuss with peers how the segment lengths correlate to making a triangle
• Students will justify their correlations by defending their findings to the class during group discussion
Vocabulary:
Includes words and phrases that are used within disciplines including: (1) words and phrases with subject-specific
meanings that differ from meanings used in everyday life (e.g., table); (2) general academic vocabulary used across
disciplines (e.g., compare, analyze, evaluate); and (3) subject-specific words defined for use in the discipline.
• Triangle
• Polygon
• Segment
• Distance/Length
• Sum
• Closed or Open
• Theorem
• Proof