Reflection: Connection to Prior Knowledge Definition of Similarity and Similar Triangles - Section 1: Launch Similarity


This initial whole-class discussion about how students decide which shape is the exception in each set is critical for building students’ conceptual understanding of similarity.  Because I wanted students to think conceptually about whether 2-D or 3-D figures are similar, I needed to ensure that they had a toolbox of ideas that made sense to them before moving forward.  One such tool I knew students would be able to bring into this lesson was their strong foundation in transformations. 

When I taught students about transformations earlier in the year, I taught them about the idea of congruence and exposed them to the idea of similarity.  For this reason, when wrapping up this whole-class discussion, I used familiar language and vocabulary from the past and encouraged students to see that similar figures can perfectly cover each other after translating, reflecting, rotating, and dilating the figures.

  Using Dilations to Make Sense of Similarity
  Connection to Prior Knowledge: Using Dilations to Make Sense of Similarity
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Definition of Similarity and Similar Triangles

Unit 12: Triangle Similarity and Trigonometric Ratios
Lesson 1 of 11

Objective: SWBAT apply the definition of similarity to identify measurements in similar figures. SWBAT to argue that HL is a “similarity shortcut” for right triangles.

Big Idea: Students' prior knowledge of transformations and congruence helps them make connections as they learn to use similarity shortcuts.

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