Math I Unit 3 Geometry - Acquisition Lesson Concept 4 - Proving Triangles Congruent

Sep 24, 2026

Uploaded by nayy☆

Lesson plan for Math I Unit 3 Geometry, Concept 4, focused on proving that two triangles are congruent. Uses an Essential Question to guide instruction, with activating strategies such as the Four Corners SSS, SAS, ASA, and AAS chart activity and vocabulary preview. Includes collaborative pair tasks using a high school pennants excerpt, graphic organizers, and distributed guided practice. Covers reasoning for SSS, SAS, ASA, and AAS, plus special cases for right triangles.

LanguageEnglish

CategoryExam

FormatPDF

Pages40

Reading Time1 h 41 min

AccessFree to download

Essential Question

Activating Strategies

Discussion

Vocabulary Teaching Strategies

Triangles Learning Task (High School Pennants)

Distributed Guided Practice/Summarizing Prompts

Summarizing Strategies

Math I Unit 3 Geometry Math 1 Unit 3 Acquisition Lesson Concept 4 Plan for the Concept, Topic, or Skill – Not for the Day Key Standards addressed in this Lesson: MM1G3c Time allotted for this Lesson: 6 Hours | Essential Question:
How can I justify that two triangles are congruent? | | --- | | Activating Strategies: (Learners Mentally Active)
Math 1 and Math 1 Support
Four Corners:
• Have adhesive chart paper placed around the room with the titles: SSS, SAS, ASA, AAS
• Give students pairs of congruent triangles which have been marked with 3 pairs of tic marks each
• Students will place each pair on the chart paper where they think it belongs
Acceleration/Previewing: (Key Vocabulary)
Vocabulary: (SSS) Side-side-side,(SAS) Side-angle-side,(ASA) Angle-side-angle,(AAS) Angleangle-side,(LL) Leg-leg,(HA) Hypotenuse-angle,(LA) Leg-angle,(HL) Hypotenuse-leg
Everyday examples of congruent items, shapes. Assembly line products: cars, water bottles, vending machine packs of M&Ms, ceiling tiles, floor tiles, concrete blocks.
As you have studied in your previous math courses, triangles can also be congruent. Use the four corners activator to discuss the corresponding sides and angles that are congruent in each set of triangles. Also, discuss why the students chose to place the triangle pairs in each of the four corners.
Based on what you know and the examples from the activator, name each pair of corresponding sides and corresponding angles if ∆BIG ≅ ∆RED.
B
• Corresponding sides – E
R
• Corresponding angles-

I G | | Discussion: What do you think is needed to prove that two triangles are congruent?
Teaching Strategies: (Collaborative Pairs; Distributed Guided Practice; Distributed Summarizing; Graphic Organizers) | | --- | | Vocabulary Teaching Strategies: Word Wall
Task : Triangles Learning Task (High School Pennants) (Questions \#1-8 only. ) Collaborative Pairs (Think-Pair-Share)
Part 1:
• Have the students read through the excerpt on hometown pennants and answer question \#1 in groups.
• Next, have students “think” through question \#2 individually.
• Then have them construct triangles as per question \#2 using prior knowledge.
• Have students “pair”with partners to discuss discoveries about “SSS”.
• After students have completed \# 2, move on to read \#3 and draw the triangles detailed in problem.
• Next, have students “pair” with partners to discuss discoveries about “SAS”.
• Emphasize that “SAS” only works when angle is between the given sides (Problem \#4) .
• Direct initial groups to pair with another group “pairs squared” and share their answers.
• Each group should compare answers and choose the best answer or incorporate their answers for a more precise answer.
• Before moving on to \# 5, have one person from each group contribute answers from \#2-4 .
• Discuss each answer as a class.
• Next, have students work through \#5 and \#6 discovering “ASA” and “AAS”. Encourage students to “think” about their answers then “pair” with their partners to ensure understanding.
• Lastly, have students read through \# 7 and “think” about how to draw triangles that work with three angles given “AAA”.
• Compare triangles with partners. Discuss whether this could be used to prove triangles congruent.
• Instruct groups to be prepared to share discoveries with the class.
Distribute “Graphic Organizer” and “Notes sheet” to ensure that students have gained necessary knowledge to continue with task. (Note: you will only need to work through part of the graphic organizer initially. As you continue with the lesson, you will complete the sheets as you go. )
Proof of AAS Theorem: See attached handout (If more is needed on the proof of this theorem, you will want to add here. )
Part 2: (Discovering special cases of congruencies for right triangles)
• Have students read through \#9- \#12 and conjecture possibilities for each. C

FAQs

How do students justify that two triangles are congruent in this lesson?

Students use congruence methods SSS, SAS, ASA, and AAS to match corresponding sides and angles, then apply the appropriate reasoning to prove triangle congruence.

What role does the Four Corners activity play?

It helps learners mentally classify pairs of congruent triangles into SSS, SAS, ASA, and AAS corners by discussing which corresponding sides and angles match and why their choices fit.

What tasks do students complete during the Triangles Learning Task?

Students read and answer questions from the pennants excerpt, construct triangles, discuss discoveries in collaborative pairs for SSS and SAS, then work through later questions to explore ASA and AAS and consider related drawing ideas.

Sep 24, 2026

Uploaded by nayy☆