## Reflection: Diverse Entry Points Using the Unit Circle to Prove the Law of Sines for Obtuse Triangles - Section 1: A Broader Conception of Angle Measure

Conceptual change is difficult...so the research says. Anyhow, I remember the first time I saw the standard G.CO 1 which has as one of its components that students will define an angle as a distance along a circular arc. Wow, I thought, what a fundamental change that's going to be from the basic idea of two rays with a common endpoint. How do you just tell someone that the definition of angle is now this? It's like trying to convince people that Pluto is not a planet when it's been a planet their whole lives.

So having some show to go with the tell is a good help. I was really happy and thankful to the creators of Sketchpad when I found a way to represent this definition of angle visually for students. So in this era when we do have the power of technology, I'm always looking for ways to visually represent concepts that are hard to understand or accept.

Good visuals help with paradigm shifts
Diverse Entry Points: Good visuals help with paradigm shifts

# Using the Unit Circle to Prove the Law of Sines for Obtuse Triangles

Unit 12: Unit Circle Trigonmetry
Lesson 3 of 5

## Big Idea: Opening up a whole new perspective on angle measures

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50 minutes