## Reflection: Advanced Students Why Do Triangles Have 180 Degrees? - Section 1: Lesson Beginning

Extension: This lesson could be more precisely defined as “why do planar triangles have 180 degrees?” I like to extend the ideas of this lesson by looking at spherical triangles and how their angle measure can exceed 180 degrees. We even demo this during the summary to remind students that we should always change the nature of a question we see in math. From the perspective of developing mathematical practices, I think that we should always ask “what if” questions. I try to change the premise of our class investigation whenever possible in order to encourage creative and flexible thinking. In my classroom I encourage students to be prepard to see where our questions lead us and explore the implications of our investigation.

Extension

# Why Do Triangles Have 180 Degrees?

Unit 5: Lines, Angles, and Algebraic Reasoning
Lesson 7 of 16

## Big Idea: Students realize that triangles are the basis for defining all angle measure.

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55 minutes

### Shaun Errichiello

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