Triangle similarity criteria (AA, SAS, SSS) and proportional sides

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Lesson Plan · Guided Notes · Exit Ticket · Re-teach · Homework

Lesson Plan →Objectives, pacing and practice, built from this lesson's brief.
Guided Notes →One page your students fill in and keep.
Exit Ticket →Three items at the end of class. No student accounts.
Re-teach →After an exit ticket: who missed what, and what to do tomorrow.
Homework →Assign practice; it grades itself.

G 603. Apply properties of 30°-60°-90°, 45°-45°-90°, similar, and congruent triangles G 703. Use scale factors to determine the magnitude of a size change

G 603. Apply properties of 30°-60°-90°, 45°-45°-90°, similar, and congruent triangles
G 703. Use scale factors to determine the magnitude of a size change

What you'll learn

Find a missing side length in similar triangles by identifying corresponding sides, setting up the proportion and solving it, including in overlapping-triangle, parallel-line-cut and shadow setups
Establish that two triangles are similar by the AA, SAS or SSS criterion
State the definition of similar triangles and explain how similarity differs from congruence
Use the scale factor k to find perimeter ratios (k) and area ratios (k^2)

Review first:

Slides

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Triangle similarity

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Practice

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Exercise

Practice problems, checked as you go

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