Reflection: Advanced Students Law of Sines - Section 6: Proving the Law of Sines for Obtuse Triangles


Originally, I hadn't planned to teach students to prove the Law of Sines for obtuse triangles, realizing that it would require students to have familiarity with trigonometry of the unit circle. As we were wrapping up our proof of the Law of Sines for acute triangles, I mentioned that the law also applies to obtuse triangles but that the proof for obtuse triangles is more complicated and requires knowledge that we don't yet have in this course.

In hindsight, I realize that by saying this, I was just stirring up the curiosity of my students who are always looking for a challenge and who always want to know more. And sure enough, one of these students stayed after the bell to ask, "So how do you prove the Law of Sines for obtuse triangles?" My answer was rushed, lacked suspense, and definitely didn't amount to a quality learning experience. I wished I had been more prepared to respond to this student in a way that would have allowed him to extend his learning in a meaningful way. So that's what inspired me to develop these later sections of the lesson on proving the Law of Sines for obtuse triangles. When I teach the lesson again, I will be prepared for the students who want to dig deeper.

  Being prepared for students who want more.
  Advanced Students: Being prepared for students who want more.
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Law of Sines

Unit 7: Right Triangles and Trigonometry
Lesson 6 of 6

Objective: SWBAT prove and apply the law of sines

Big Idea: Looking for a sine? In this lesson, students will prove the law of sines and use it to solve problems.

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law of sines diagram
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