An Area Formula for Triangles

Use a triangle area formula that works when the height is unknown. The eighth installment in a 16-part series on trigonometry revisits the trigonometric triangle area formula that previously was shown to work with the acute triangles. Individuals verify that the formula works for all triangles using the sine function as opposed to the sine ratio.

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CCSS: Designed
Instructional Ideas

  • Have groups calculate the areas of triangles using the traditional formula from middle school and the new formula to confirm they both provide the same area
  • Review decomposing figures into triangles to determine areas
Classroom Considerations

  • The class should be familiar with the trigonometric formula to find the area of acute triangles
Pros

  • The problem set starts with finding areas of triangles to applying the concept to solve more complex problems
  • Resource highlights where mathematical practices are used in the lesson
Cons

  • None
Common Core