Reflection: Student Feedback Law of Cosines - Section 4: Deriving the Formula


Of all the lessons I taught this year, this was the one that caused the most complaining on the part of students. Many students said they were completely lost, complained that I was not teaching, and generally seemed to be rejecting the lesson.

Interestingly, months later in preparation for Open House, I asked students to choose one artifact from the entire year that they would like to showcase, many of these same students chose the work they had done deriving the Law of Cosines. The students had to write a short caption explaining why they chose the artifact. The captions for this lesson had some common features. Students said they were proud that they had persevered and overcome their initial confusion in order to complete the task (MP1). Students were proud that they had achieved something that they perceived to be very difficult. This gave them a real sense of accomplishment. Students were proud of the way they were able to not only do the work, but to explain it.

This taught me that I have to stick to my guns when I am trying to get students to do something that is truly challenging. Although there will be pains and grumblings, and although it will take hard work and perseverance on my part and theirs, the payoff in terms of students'  sense of self-efficacy is great when the task is accomplished.



  Challenging Tasks and Self-Efficacy
  Student Feedback: Challenging Tasks and Self-Efficacy
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Law of Cosines

Unit 7: Right Triangles and Trigonometry
Lesson 5 of 6

Objective: SWBAT derive the law of cosines formula and use it to solve problems

Big Idea: Deriver's...start your engines!...In this lesson, we'll be doing some heavy duty mathematics to derive the Law of Cosines.

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