Reflection: Developing a Conceptual Understanding SAS Area Formula - Section 1: Developing the formula


Teaching decision-making is one of my overarching goals in the geometry course. In this lesson, students should continually be in decision-making mode. For example, they should be deciding:

  • which base is most efficient to use for a particular triangle (regardless of its orientation),
  • which height corresponds to a particular base,
  • whether to use Pythagorean Theorem or trigonometry to find the height,
  • whether it is even possible to find the height,
  • under what circumstances we should apply the formula 
  • whether trigonometric ratios apply to all triangles

In order to get students to ask themselves these questions, I have to model this decision-making process by thinking out loud and being explicit about all decisions I make in the problem-solving process and my reasons for making them.

  Decision Making
  Developing a Conceptual Understanding: Decision Making
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SAS Area Formula

Unit 7: Right Triangles and Trigonometry
Lesson 4 of 6

Objective: SWBAT to derive and apply the formula for finding the area of a triangle given two side lengths and the included angle measure.

Big Idea: Batteries not included...but the angle must be. Some assembly required. In this lesson students build a new triangle area formula and learn when and how to apply it.

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3 teachers like this lesson
Math, Trigonometry, Geometry, Triangles, right triangle, Triangle Area
  55 minutes
triangle diagram
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