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Lesson Title: 5.1 Congruent Triangles
Lesson Length: 2 days
HSCEs: G2.3.1
Lesson Objectives: Students will be able to determine if two triangles are congruent
based on the congruent postulates or theorems.
Lesson Opener: What does the term congruent mean? Give a picture of a triangle and
have them label/pick out the “sides” and the “angles”. Ask them to point the side
opposite a specific angle. Ask them how to label the points (small case or upper case).
Definitions/Vocabulary to Cover: side, angle, right angle, hypotenuse, leg, reflexive
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Examples to Cover:
Is there enough information given to prove the triangles are congruent? If so, state the
postulate or theorem.
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Lesson Title: 5.2 Proving Triangles are Congruent
Lesson Length: 1 day
HSCEs: G.2.3.1, G.2.3.2
Lesson Objectives: Students will be able to write proofs regarding congruent triangles.
Lesson Opener: What does the term congruent mean? Draw two apparently congruent
triangles….now mark sides & angles to make them congruent. What if you weren’t
given all the necessary information, what would you need to do?
Definitions/Vocabulary to Cover: midpoint, congruent, parallel, lines cut by a
transversal, parallel lines cut by a transversal, reflexive property
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Special Note: you may want to revisit doing a 2 column proof using algebraic equations.
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Lesson Title: 5.3 Similar Triangles
Lesson Length: 1 day
HSCEs: G2.3.3, G2.3.4, G2.3.5
Lesson Objectives: Students will be able to show triangles are similar using the correct
postulate or theorem.
Lesson Opener: What does the term similar mean? Is everyone in this room similar to
each other? In what way? How do you think the terms “similar” and “congruent” are
related?
Definitions/Vocabulary to Cover: similar, similarity statement, ratio, scale factor,
proportion.
Examples: Are the triangles similar? If so, list the congruent angles. Is so, what is the
scale factor?
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State if the triangles are similar. If so, write the similarity statement and the
postulate or theorem.
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Lesson Title: 5.4 Using Similar Triangles
Lesson Length: 1 day
HSCEs: G2.3.4, G2.3.5
Lesson Objectives: Students will be able to find the missing measurements using similar
triangles.
Lesson Opener: What does the term similar mean? Can a triangle have side lengths: 12,
14, 5 while another triangle has sides 12, 14, 10 and still be considered similar? If you
know two triangles are similar and triangle A has sides 13,15, x but you know the second
triangle is twice as big, can you determine the side lengths of triangle B?
Definitions/Vocabulary to Cover: similar, ratio, scale factor, proportion
Examples:
1. Find KJ
3. Solve for x.
2. What is the scale factor?
4. Solve for x.
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